Exhaust changes causes problems

[rogerzr1]

I just replaced the stock exhaust with B&B and X pipe. The car seems to stumble in low rpm and hesitates a little during acceleration. The car acts like it wants to backfire, but doesn't. Any ideas?:pray

[GOLDCYLON]

I just replaced the stock exhaust with B&B and X pipe. The car seems to stumble in low rpm and hesitates a little during acceleration. The car acts like it wants to backfire, but doesn't. Any ideas?:pray

Did you remove the factory cats?

[rogerzr1]

Did you remove the factory cats?

No. The factory cats are still in place.

[GOLDCYLON]

No. The factory cats are still in place.

Hmm well if they were I would suggest a chip change however since they are not Im assuming a stock chip?

[rogerzr1]

Hmm well if they were I would suggest a chip change however since they are not Im assuming a stock chip?

I have a Chip from Marc Haibeck. It was tuned for a stock setup. Would an exhaust change like this require a reprograming? I figured I wouldn't need a reprogram until I put headers on it.

[Hammer]

I am getting ready to put headers on. Watson's I think. I have the Haibeck chip and am expecting to have to have it reprogrammed. I have heard I can expect backfiring without cats but that can be programmed out.

So far:
K&N with Open lid
Flowmaster Catback
Haibeck Chip

Once the headers are on (a couple weeks) I'll post the results.

[GOLDCYLON]

I have a Chip from Marc Haibeck. It was tuned for a stock setup. Would an exhaust change like this require a reprograming? I figured I wouldn't need a reprogram until I put headers on it.


I would not think so with the cats one I would ask Marc if it is his chip

[bradslt5]

I believe that mark pulls just a little fuel out of his base prom. . if you got the 3in bandb you could be running just alittle lean . are you using 91 or 93 oct fuel . also remember that this time of year they put more ethanol in the fuel this is a winter thing .

[bradslt5]

also you might want to ck your fuel pressure to see if everything is ok . how long has it been since you changed your fuel filter ? hopes this helps

[rogerzr1]

also you might want to ck your fuel pressure to see if everything is ok . how long has it been since you changed your fuel filter ? hopes this helps

Good idea. I just got the car back in July. How hard is it to change the fuel filter?:icon_scra

[GOLDCYLON]

Good idea. I just got the car back in July. How hard is it to change the fuel filter?:icon_scra

20-25 min job flare wrenches make the job easier

[Jeffvette]

One thing to check as well is for exhaust leaks. Those will create some of the problems you are describing as well.

[tomtom72]

Roger, the fuel filter is over on the frame rail on the right side next to that cat....well sort of next to the cat. Ya can't see it too clearly as there is a heat shield that hides most of it.

I usually do that when I do my season "get ready" so I have the car up on 4 stands, makes for one trip to do all my underside stuff. Anyway, one stand under the right front rail where it turns in should do it.
Remove gas cap.

bleed off any pressure at the front of the right fuel rail schrader valve with rag to catch fuel or if ya got a gauge with a bleed line your gold.

Use a catch basin under the filter anyway, or a rag. I always get some spillage.

Take off the two bolts that hold heat shield....mm, 10 or 13.

Using Line wrenchs on the filter and line 19 & 19 or 19 & 20 mm(?). Hold filter with one wrench and undo the line with the other wrench at "in" & "out".

Remove the filter band clamp bolt, 10mm & remove filter.

Reverse to install new filter. Leave car up and KOEO to test for leaks. Heat shield back on. Lower car.:wink:

Go for test drive, then have beer!:mrgreen:

:cheers:
Tom

[GOLDCYLON]

One thing to check as well is for exhaust leaks. Those will create some of the problems you are describing as well.

Good point !

[bradslt5]

Jeffs got a good idea too. you might want to test for the exhaust leaks when you do the fuel filter. that is only if you jack the whole car up in the air with 4 jackstands under the car . do you have the zr1 bible (helms manual) they are just over a hundred bucks and very worth it . also worth considering is a scann tool to dk for codes that may pop up from time to time. congrats on your new ride . these are very special and cool rides:thumbsup:

[rogerzr1]

I appreciate everyone's help. I talk to Marc H today. He thinks it may be a sparkplug or ignition problem. He doesn't think that what is going on is a result of the new exhaust. Since I had recently changed the sparkplugs he said it might also be fuel related. He said to hook up a long hose and a gauge and drive it around to see what the fuel presure measures. If someone could give me an idea how to pull this off, I would like to try it. BTW I just drove the car for about 15 minutes and it didn't seem to hesitate as bad(then it started snowing). Don't know if this means anything or not. Looks like the fuel presure is as good a place as any to start. Please help.:pray

[XfireZ51]

roger,

When you say that it feels like it almost wants to backfire, what exactly do you mean by that? What is it doing? Can you be more specific?

[rogerzr1]

roger,

When you say that it feels like it almost wants to backfire, what exactly do you mean by that? What is it doing? Can you be more specific?

In talking with Marc, the backfire issue doesn't seem to be a problem. I am use to hearing the stock exhaust. He said what I was hearing had always been there, I just didn't hear it as bad. The real problem is that in low rpms the car seems to hesitate more and at WOT it was stumbling at around 4500 rpms. Once past that it was fine. It almost seems like maybe the engine isn't getting enough gas, I don't know. I feel stupid not being able to describe the situation better or know more about what is going on.

[Pete]

What kind of plugs and where did you gap them?

Pete

[rogerzr1]

What kind of plugs and where did you gap them?

Pete

They were the recomended AC DELCO part. I can't remember the part number. The mechanic said they were the right ones. I also had a new spark plug wire set to put on the car, but the mechanic said the ones on the car where ok. I wish he had changed them, at least I would feel better about it knowing the wires were new.

[XfireZ51]

Roger,

Its possible that the less restrictive exhaust may have caused the AFR to lean out somewhat. Can you get a scantool on it? The 4500rpm region is where you might expect Knock Retard to come in and the hesitation could be the ECM pulling timing out.
Just possibilities which need to be verified by a scan.

[rogerzr1]

Roger,

Its possible that the less restrictive exhaust may have caused the AFR to lean out somewhat. Can you get a scantool on it? The 4500rpm region is where you might expect Knock Retard to come in and the hesitation could be the ECM pulling timing out.
Just possibilities which need to be verified by a scan.

I am new to all this, I will see if any of the z guys around me have a scantool that might be willing to help. I just ordered the Helms manual, so that shows you I am little behind.

[bradslt5]

you might want to invest in a setof ngk irridiums. i switched to them and just love em

[cuisinartvette]

Hypertech makes a fuel gauge with a hose long enough you can gently shut the hood on it and still see the gauge while you drive. Screw one end on the shrader valve (make sure it dont leak) and watch the gauge under load.

[rogerzr1]

Hypertech makes a fuel gauge with a hose long enough you can gently shut the hood on it and still see the gauge while you drive. Screw one end on the shrader valve (make sure it dont leak) and watch the gauge under load.

Thanks for the info. Sounds like something I can pull off. Where is the best place to buy a Hypertech fuel gauge? I have looked on line and can't find one for a 91 corvette.

[cuisinartvette]

I think I bought mine from Mid America Motororks, Im sure there are cheaper places some of the guys know of but thats where I got mine.

[Polo-1]

lazy 02 sensor.
New free flow exhaust, 02's are not warming up as fast or staying cool.

Just a guess.:wink:

[Pete]

Correct me if i'm wrong,we have heated O2's and they are on the OE CAT/manifolds.

Also to run lean with CATS on i don't think that would be unless bad pump filter or injectors.
Our Z's run a bit rich from the factory around 12.6-12.8 AFR
I don't really think his running that lean to cause it with just an exhaust install since he also kept the CATS
Look at Marc H's web site on this.

Heck i ported the heck out of my intake,heads,63mmTB,headers,B&B's
X-pipe no/CATS and still didn't need to adjust fuel.

Pete

[rogerzr1]

Something else I didn't think too much about was the last couple of times I was letting the car warm up, it died. This has never happened before, but I just thought it was the cooler weather. The thing is it died after about 3 minutes. Could this be fuel related rather than cooler weather related?

[A26B]

Sounds like primary fuel pump problem. When cold started, both the primary & secondary fuel pumps operate until the coolant temp reaches 167F, then the secondary pump shuts off.

You need to run the fuel pressure check described above.

[bradslt5]

BINGO. i agree with the above . ebay has a real deal on fuel pump assemblies. but i remember in the bible it talking about one of the fuel pumps turning off as stated above . good catch :thumbsup:

[rogerzr1]

If it is a primary fuel pump, would I need to drive it to get the fuel presure or would it show the problem at idel. The reason I ask this is that I am having a hard time finding a fuel presure gauge that has a long enough hose to drive and check it.

[Pete]

If it is a primary fuel pump, would I need to drive it to get the fuel presure or would it show the problem at idel. The reason I ask this is that I am having a hard time finding a fuel presure gauge that has a long enough hose to drive and check it.

Try this first,hold both heater up & down arrow buttons for 5 seconds you will see 00 let them go and just hit the up arrow till you see 16 now hit auto button that will be your engine temp in celcius let your car idle till it hits 75 celcius if it dies then the primary pump is gone.
We have 2 pumps both are on at cold start up @ 169 F secondary shuts off.


Pete

[bradslt5]

great explanation on how to use the airconditioner for temps i allways wondered how to do that =D>

[Jeffvette]

If it is a primary fuel pump, would I need to drive it to get the fuel presure or would it show the problem at idle. The reason I ask this is that I am having a hard time finding a fuel presure gauge that has a long enough hose to drive and check it.

Well, all you really need to do is pull the secondary fuel pump fuse and keep a gauge on the rail and key on. Pump should run for about 2-3 seconds and pressure should be between 48-5 psi and hold after the pump stops running.

If you can find just a gauge, and hydraulic hose shop can build you a custom length hose.

[Pete]

Well, all you really need to do is pull the secondary fuel pump fuse and keep a gauge on the rail and key on. Pump should run for about 2-3 seconds and pressure should be between 48-5 psi and hold after the pump stops running.

If you can find just a gauge, and hydraulic hose shop can build you a custom length hose.

My way is the lazy way just sit back listen to tunes and have a beer.:p

Pete

[XfireZ51]

My way is the lazy way just sit back listen to tunes and have a beer.:p

Pete

:sign10:

[rogerzr1]

Try this first,hold both heater up & down arrow buttons for 5 seconds you will see 00 let them go and just hit the up arrow till you see 16 now hit auto button that will be your engine temp in celcius let your car idle till it hits 75 celcius if it dies then the primary pump is gone.
We have 2 pumps both are on at cold start up @ 169 F secondary shuts off.


Pete

I did what you said Pete(pretty cool btw). The car didn't shut off at 75. I decided to take it for a drive with the power key off. It drove like sh**. When I applied the gas, the car shuttered and vibrated for a couple of seconds then smoothed out. My question is even though the car didn't shut off at 75, can the primary fuel pump still not be preforming correctly. Just wanted to see if this rang a bell with anyone. I plan on getting a guage tomorrow and trying what Jeff said to do.

BTW I appreciate everyone's help trying to educate my ignorant a**.;)

[XfireZ51]

Roger,

Have you checked injectors?

[rogerzr1]

Roger,

Have you checked injectors?

Injectors were all changed in August.

[XfireZ51]

And?

[Pete]

I did what you said Pete(pretty cool btw). The car didn't shut off at 75. I decided to take it for a drive with the power key off. It drove like sh**. When I applied the gas, the car shuttered and vibrated for a couple of seconds then smoothed out. My question is even though the car didn't shut off at 75, can the primary fuel pump still not be preforming correctly. Just wanted to see if this rang a bell with anyone. I plan on getting a guage tomorrow and trying what Jeff said to do.

BTW I appreciate everyone's help trying to educate my ignorant a**.;)

Yes,the primary could be performing poorly,you also have to remember the secondary Feul Pump will kick on at a certain throttle point.
I would then also try what Jeff said,take the secondary FP fuse out and try again,should have the stumble all the time if it's the primary.
If it turns out you do need FP just get one from a 1996 Chevy Truck 2500 the one with 454ci big block.
Pete

[Pete]

And?

I'l add to this some injectors can Ohm out good but could leak like a fire hose.
To check this without a pressure gauge turn ignition to the on position and do a visual or have someone else keep an eye on the injectors while you turn ignition on.


Pete

[XfireZ51]

Pete,

That was my point. Having replaced injectors in August doesn't eliminate them as a problem. Thanks for clarifying that even ohming out injectors may not be enough. Wouldn't there be a gas smell if the injectors were leaking or plugs showing raw fuel?

[rogerzr1]

Pete,

That was my point. Having replaced injectors in August doesn't eliminate them as a problem. Thanks for clarifying that even ohming out injectors may not be enough. Wouldn't there be a gas smell if the injectors were leaking or plugs showing raw fuel?

I haven't smelled any gas smells. I am in no position to not listen to all of you all's sugestions. I was hoping that I could elimenate the injectors as a possible problem being they are new, but obviously I can't. I just want to get this thing figured out.

[Jeffvette]

I'l add to this some injectors can Ohm out good but could leak like a fire hose.
To check this without a pressure gauge turn ignition to the on position and do a visual or have someone else keep an eye on the injectors while you turn ignition on.


Pete

Correct, just because they spec out in ohms, does not mean there is a issue with them being stuck open or closed or dribbling. I've had a few like that.

[Pete]

I just replaced the stock exhaust with B&B and X pipe. The car seems to stumble in low rpm and hesitates a little during acceleration. The car acts like it wants to backfire, but doesn't. Any ideas?:pray

Roger,have you done anything else to the car recently besides exhaust.

The symptoms you describe sound like bad spark plug wires,spark plugs or injectors.

You know what's funny is half the guys on here, had the car in front of them or took it for a test drive would figure it out in a second.

Pete

[rogerzr1]

Roger,have you done anything else to the car recently besides exhaust.

The symptoms you describe sound like bad spark plug wires,spark plugs or injectors.

You know what's funny is half the guys on here, had the car in front of them or took it for a test drive would figure it out in a second.

Pete

I know, that's what is killing me. The injectors and spark plugs were changed in August. The spark plug wires were not changed.

The best I can describe it is:

As I step on the gas there is a little hesitation.
As the car speeds up it seems to catch back up and perform correctly until 3rd gear around 4500rpms it jerks (like there is no fuel) then continues to accelerate.

I don't know how better to describe it. When the power key is off, the car shakes and hesitates as I step on the gas. It seems like when the key is on, it makes the car drive better but it seems its just masking the real problem.

I don't know, now I am confusing myself.:o

[Jeffvette]

Were the injectors replaced or were they cleaned?

[rogerzr1]

Were the injectors replaced or were they cleaned?

I had them replaced with the Accel injectors.

[Jeffvette]

ok, just grasping at straws since the car isn't in front of me.

Wonder if they put the injectors in correctly, meaning they used the top indent for the c clip.

I would start looking at spark. This is when a scan tool is handy. Just makes it all the easier when you can see fuel trims, knock counts and 02 fluctuations.

[rogerzr1]

ok, just grasping at straws since the car isn't in front of me.

Wonder if they put the injectors in correctly, meaning they used the top indent for the c clip.

I would start looking at spark. This is when a scan tool is handy. Just makes it all the easier when you can see fuel trims, knock counts and 02 fluctuations.

I just have ordered the Helms maual, no scan tool. Should I go ahead and get the fuel gauge and check that or does it not sound like a fuel issue?

[Pete]

Roger,if you have a digital camera take pictures.
Close up of what Jeff mentioned the injectors,unplug a primary and take a close up.

I would change the Wires.

Pete

[rogerzr1]

Roger,if you have a digital camera take pictures.
Close up of what Jeff mentioned the injectors,unplug a primary and take a close up.

I would change the Wires.

Pete

Problem is I have never taken the plenum off. I had the other work done and can't afford ($) to take it back to the guy right now. I guess I could try a plenum removal.

[Gunny]

Problem is I have never taken the plenum off. I had the other work done and can't afford ($) to take it back to the guy right now. I guess I could try a plenum removal.

Plenum not hard after you've done it once. Actually, it's not hard the first time, but a little scary since you don't want to mess anything up.

Get your tools together, the Helms manual, and a WARM place to work and you're all set.

btw, where in Georgia are you?

George
1990 #2957 black/black

[bradslt5]

roger, i think jeff has apicture guide on plenum removal, but not totally sure . I ampositive he could guide you through it . the process is alot easier than you might think . you just have to go slowly and make sure you remove all 4 electrical connectors that are under the plenum 2 from the front and 2-3 from the back 3 if one includes the map sensor . you dont have to seperate the throttle body from the plenum. it comes off in one big piece . but the decision to do it is up to you .is there anyone close that could help this nice guy out ?

[rogerzr1]

Plenum not hard after you've done it once. Actually, it's not hard the first time, but a little scary since you don't want to mess anything up.

Get your tools together, the Helms manual, and a WARM place to work and you're all set.

btw, where in Georgia are you?

George
1990 #2957 black/black

I live in Cartersville. I wanted to maybe watch plenum removal a couple of times before I tried, but looks like that won't be the case.

[cuisinartvette]

Its not really involoved, you can do it. Links here to help you out. Take your time, observe and go slowly.

[rogerzr1]

Ok guys, I checked the fuel presure. Here is what I found:

With key on(no engine on) - 46# about 20 minutes later 30#

With key on(no engine on and seconary fuse pulled) - 48# 20 minutes 36#

WIth the engine on - 44# at idle car off presure at 44# for 20 minutes

I don't know what any of this means.
Does any of it make sense?

[A26B]

Roger,

Data indicates the problem is probably not with the fuel pumps.

Few questions:
1. Did you ever change the fuel filter?
2. Did you ever experience any of these symptoms, before installing the new exhaust system?
3. Have you pulled the stored codes?
4. Are you getting any warning lights on the display?

[rogerzr1]

Roger,

Data indicates the problem is probably not with the fuel pumps.

Few questions:
1. Did you ever change the fuel filter?
2. Did you ever experience any of these symptoms, before installing the new exhaust system?
3. Have you pulled the stored codes?
4. Are you getting any warning lights on the display?

1. The fuel filter was changed back in August.
2. There were a couple of times that the car did hesitate, but I just thought it was the nature of the beast. One thing I thought of is that the car is more prone to act up if there is another person in the car with me. I can't imagine another 180lbs would cause any problems. Just trying to give all the info I have.
3. I don't have a scan tool.
4. I have not had any lights come on except the service ride control. It comes on if I let the car idle for a while, but goes away when I start driving.

I am going to show my extreme ignorance now - I paid close attention when I started the car the last time. There was a vacume type sound and I felt a lot of air under the left coolant conector. After a couple of minutes the sound went away and the air flow did too. This is probably normal and I should know it, but I just thought I would mention it.

Again, let me thank all of you who are trying to help. I really appreciate it.:worship:

[Scottys72]

Hi Roger - I found this link for removing the plenum in another post:

http://www.bcvettes.org/

Look under "How To"

Good luck

Scott

[Jeffvette]

I am going to show my extreme ignorance now - I paid close attention when I started the car the last time. There was a vacume type sound and I felt a lot of air under the left coolant conector. After a couple of minutes the sound went away and the air flow did too. This is probably normal and I should know it, but I just thought I would mention it.

Again, let me thank all of you who are trying to help. I really appreciate it.:worship:

The vacuum noise is the air injection system. I would not expect you to be feeling any air other than what is coming off the serp belt system and power steering pulley right in that area.

[rogerzr1]

The vacuum noise is the air injection system. I would not expect you to be feeling any air other than what is coming off the serp belt system and power steering pulley right in that area.

If the air I was feeling is coming from the serp belt or power steering pulley would it go away after a couple of minutes or would it be there the whole time the engine is on?

It is a very noticable amount of air flow.

[rogerzr1]

Hi Roger - I found this link for removing the plenum in another post:

http://www.bcvettes.org/

Look under "How To"

Good luck

Scott

Thanks Scott. I looked it over. I don't feel quite as scared as I was before. I think with a step by step guide I can pull it off. The only problem is I don't really know what I am looking for under the plenum.

I drove the car this evening and actually had it backfire on me. I drove it around for a while to let it warm up and it drove fine. After it warmed up I gave it a few WOT. A couple of times it drove great. One time it backfired in 1st at 5500 rpms, then drove like it was turbocharged through 3rd. I am so confused.

[Jeffvette]

If the air I was feeling is coming from the serp belt or power steering pulley would it go away after a couple of minutes or would it be there the whole time the engine is on?

It is a very noticable amount of air flow.

It should not go away if it's coming from the belt and pulley. I'll give you a call in a few mintures Roger.

[rogerzr1]

It should not go away if it's coming from the belt and pulley. I'll give you a call in a few mintures Roger.

Jeff,

Please give me a call when you get a chance. Do you still have my number?

[Polo-1]

Sounds a lot like my Z.

Replace the 02 sensors. Easy and cheap to do. Also check the TPS with VOM.

[rogerzr1]

Sounds a lot like my Z.

Replace the 02 sensors. Easy and cheap to do. Also check the TPS with VOM.

My Helms manual should be here next week. I hope it will describe how to do what you have suggested.

I plan on taking the plenum off and will more than likely change the plugs and the plug wires. I have a set of the AC Delco plug wires. Should I go with the NGK plugs? :icon_scra

Another question: Any chance my ECM is the problem. Seems like I read before that a couple of guys had a simular problem that replacing the ECM fixed.

[rogerzr1]

Sounds a lot like my Z.

Replace the 02 sensors. Easy and cheap to do. Also check the TPS with VOM.

My Helms manual should be here next week. I hope it will describe how to do what you have suggested.

I plan on taking the plenum off and will more than likely change the plugs and the plug wires. I have a set of the AC Delco plug wires. Should I go with the NGK plugs? :icon_scra

Another question: Any chance my ECM is the problem. Seems like I read before that a couple of guys had a simular problem that replacing the ECM fixed.

[ShawnZR-1]

Roger, if you need a hand, let me know. I'm in north Georgia but I'm always up for traveling to help out a fellow ZRoner!

I have DIACOM and can scan your car if need be.

[ShawnZR-1]

Roger, if you need a hand, let me know. I'm in north Georgia but I'm always up for traveling to help out a fellow ZRoner!

I have DIACOM and can scan your car if need be.

[bradslt5]

just thought to share . thats a really cool offer you made to him. makes me glad to see so many that go out of their way to help others here:thumbsup: :thumbsup: now if the world would only do the same.....................

[rogerzr1]

Roger, if you need a hand, let me know. I'm in north Georgia but I'm always up for traveling to help out a fellow ZRoner!

I have DIACOM and can scan your car if need be.

Shawn, thanks. I was hoping that you or Steve had a scan tool and would offer to help.:D

The first thing I am going to do is replace the o2 sensor. If this doesn't fix the car, I am lost and would love some help. I will drive to you if that works better, but lets see what the o2 change does.

Even if the o2 fixes the problem, I still would like to meet you and Steve.

[Tyler Townsley]

I posted this in another thread but it is some simple things any owner can do to help people trying to do troubleshooting from afar.

1. Compression check.
2. Run the car, park it and look at the plugs they should be uniform in appearance if not then chase fuel/spark on that cyl.
3.Take a good known plug and one cyl at a time unplug the wire, plug in the plug, lay it on the plenum and start the car. The spark should be the same on every cyl if not then you know which coil pack/wire to chase for problems.
4. There is a DIS checker and should you suspect the dis of falling apart I can lend it to you. You need some kind of a scope to look at the signals to verify its falling apart.
5. If you pull the plenum then you can check the injectors by pulling fuel rail up, crank the car and look at the spray pattern.
6. If you have a suspect cyl you can eliminate spark with step 2 and check fuel by swaping injectors from cyl to cyl, this requires pulling the plenum but you get pretty good at in with practice.
7. Listen for the vacuum pump at the left front of the car. You should hear it cycle for a couple of seconds when the key is first turned on the go quiet for at least 5-10 minutes. Both failing to pull the vacuum, on start and an continuly cycling pump signal problems that will cause what you describe.

Let us know what you find.

Tyler

[ShawnZR-1]

Shawn, thanks. I was hoping that you or Steve had a scan tool and would offer to help.:D

The first thing I am going to do is replace the o2 sensor. If this doesn't fix the car, I am lost and would love some help. I will drive to you if that works better, but lets see what the o2 change does.

Even if the o2 fixes the problem, I still would like to meet you and Steve.
Oh, I bet I can sucker Steve into a mini-gathering! :)

Just let us know what the outcome is on the O2 sensor change. :hello:

[rogerzr1]

Changed both o2 sensors. After I changed the left one(couldn't get to the right one) the car drove pretty good. I drove it one night I guess the temperature was around low 40's. The reason I mention this is that I have now changed the right side o2 sensor and the car is still having problems. I drove it today, temp around upper 50's and it hesitated at WOTH about 20% of the time. It is driving better than before I changed the o2 sensors, but not as well as it drove before the right o2 sensor.

Could I be looking at something that is related to outside temp or am I just grasping at straws.

Any body have any dynamite?;)

[bradslt5]

roger , let me ask a couple of ?s when you turn the key to on not star do you here the motor for the vaccume pump come on in thge right front up by the headlight . does it go on and shut off or does it cycle on and off?. did you ever get the helm manual yet ? if not you really need one it would help you alot in deducing your problems .pm me if you still need help and i will seeif i i can walk you thru some ideas to help brad

[rogerzr1]

roger , let me ask a couple of ?s when you turn the key to on not star do you here the motor for the vaccume pump come on in thge right front up by the headlight . does it go on and shut off or does it cycle on and off?. did you ever get the helm manual yet ? if not you really need one it would help you alot in deducing your problems .pm me if you still need help and i will seeif i i can walk you thru some ideas to help brad

The vaccume comes on and then goes off. I am not sure about it cycling on and off, I will check. I do have the Helms manual.

I never checked the fuel filter. Any chance there is something with that?

[bradslt5]

could be . have you cked your fuel pressure? when i get a car the first thing i do is change all filters and fluids then i know everything is fresh . does it stumble when you first floor it or towards the top end of the rpm scale ?

[rogerzr1]

roger , let me ask a couple of ?s when you turn the key to on not star do you here the motor for the vaccume pump come on in thge right front up by the headlight . does it go on and shut off or does it cycle on and off?. did you ever get the helm manual yet ? if not you really need one it would help you alot in deducing your problems .pm me if you still need help and i will seeif i i can walk you thru some ideas to help brad

Just checked the car. Now the vaccum is not coming on when I turn the key. I know it was working before I took my drive. Any idea what happened. Is there an easy way to tie the secondaries open to check if this is the problem or if its just another problem?

When I turn the key the vaccum makes two little noises and then doesn't do anything.

Seems like I get one thing fixed and something else breaks. Anyone found any of that dynamite for me yet?

[rkreigh]

where in Ga are you???

SGC is in thomasville and can take some headache away if you don't want to work on the car. one thing I found which can be embarrasing but it's common. if the injector wiring isn't clipped on securely they can pop off!!

you then have one or more secondary injectors that don't get any juice!

you can check for this by ohming out the injectors with the plenum still on

see

www.zr1specialist.com (http://www.zr1specialist.com)

for the procedure

the exh probably doesn't have anything to do with it, as mentioned above it's just letting you hear what you didn't before, and if you were a bit lean before, you are a bit leaner now!!

the stock chip should work fine. definitely need to change that other 02. one new and one old isn't a good idea, they are hard to get to. just another reason to put those headers on!

good luck. my bet is that you have a bad plug wire or coil pack. fairly common.

you can test that by pulling one plug wire at a time and putting a grounded plug in the wire. when you see a weak spark, you typically found out which is misfiring.

pull the plugs and have a good look at them, they reveal alot. if the injectors are leaky (probably not) you can often smell it from that cyl with the plug out.

the lt5 isn't that tough to work on, just be patient and get the factory service manual to keep you on track. has some great troubleshooting flowcharts that really help.

[bradslt5]

Just checked the car. Now the vaccum is not coming on when I turn the key. I know it was working before I took my drive. Any idea what happened. Is there an easy way to tie the secondaries open to check if this is the problem or if its just another problem?

When I turn the key the vaccum makes two little noises and then doesn't do anything.

Seems like I get one thing fixed and something else breaks. Anyone found any of that dynamite for me yet?roger ,there is a fuse on the driver side of the car just in front of the brake master cylinder on the inside of the wheel well its a 10 amp its for the vaccume pump. it may be blown as mine was

[rogerzr1]

roger ,there is a fuse on the driver side of the car just in front of the brake master cylinder on the inside of the wheel well its a 10 amp its for the vaccume pump. it may be blown as mine was

Ok, checked the inline fuse, it was fine. Is there anything else I should check electrically for the vacuum pump.

Again, when I turn the key the pump now clicks twice. Before it use to run for a couple of minutes.

[Jeffvette]

Pull the vacuum hose off at the bottom of the pump. But your problem does not lie here. Take one thing at a time.

Roger, I'll give you a shout in a few.

[rogerzr1]

Pull the vacuum hose off at the bottom of the pump. But your problem does not lie here. Take one thing at a time.

Roger, I'll give you a shout in a few.

What do I need to do next. I drove the car tonight and it drove pretty good. I don't hear the vacuum when I turn the key, but it sure seems like the secondaries are working.

[bradslt5]

roger ,pull the connection off the vaccume pump then go and turn on the ignition and listen for the pump to turn on . if it doesnt run all the time with the hose off it could have a problem. here is where i have a tough time i dont know how to show you the link on that stuff . i can bearly type . on corvette action center in the zr1 area is a good thread on the secondary system and the vACCUME PUMP TOO. hope nthis help s going to get busy . grass is getting ready to grow , have to paint the new house after work . wife a has found a new toy this foam that is so light you cant feel it till it oooozes out of things like gloves hats shoes . i gotta be the only married guy in the world whose pregant wife turned into the biggest prankster ever born. sure is fun:o

[rogerzr1]

roger ,pull the connection off the vaccume pump then go and turn on the ignition and listen for the pump to turn on . if it doesnt run all the time with the hose off it could have a problem. here is where i have a tough time i dont know how to show you the link on that stuff . i can bearly type . on corvette action center in the zr1 area is a good thread on the secondary system and the vACCUME PUMP TOO. hope nthis help s going to get busy . grass is getting ready to grow , have to paint the new house after work . wife a has found a new toy this foam that is so light you cant feel it till it oooozes out of things like gloves hats shoes . i gotta be the only married guy in the world whose pregant wife turned into the biggest prankster ever born. sure is fun:o

Brad, I checked the vacuum pump and it turns out it is working fine.

I talked with Jeff and he thinks it could be a few things. I am going to try and elimenate them one by one.

Sounds like you are going to be a busy man pretty soon. Your wife sounds like quite a gal. I guess you have to watch everything you put on, or it might have a suprise in it.:mrgreen:

[Sgreg]

I had a few of the same symptoms and guess what; it turned out one of the crappy rachet plastic clamps came off a fuel pump hose allowing fuel to be pumped around the tank instead of to the injectors. Replaced plastic clamps with stainless clamps and all was well. Just another possibility.

[rogerzr1]

Just got back from about a two hour drive in the Z. The car didn't stumble at all during WOT. :D

The Z still has a pretty good hesitation at lower rpms. The acid test, as Paul Workman put it, low rpms and floor it, my car stumbles every time.

Jeff did you get my pm with my address?

[Jeffvette]

Yep I did. ECM is on it's way monday.

[XfireZ51]

I did what you said Pete(pretty cool btw). The car didn't shut off at 75. I decided to take it for a drive with the power key off. It drove like sh**. When I applied the gas, the car shuttered and vibrated for a couple of seconds then smoothed out. My question is even though the car didn't shut off at 75, can the primary fuel pump still not be preforming correctly. Just wanted to see if this rang a bell with anyone. I plan on getting a guage tomorrow and trying what Jeff said to do.

BTW I appreciate everyone's help trying to educate my ignorant a**.;)


Just re-reading these posts. Sounds like a fuel issue to me but its not the fuel pump or filter. He has backfiring on decel and stumble at tip-in which sounds like a lack of AE. I would suspect TPS or CTS. My $.02.

[rogerzr1]

Yep I did. ECM is on it's way monday.

Jeff, just checking to see if you had a chance to send the ECM. I was hoping to possibly get the car running good before the Meeting in AL. I know it may not be the ECM, but it seems like the best place to start before I take the plenum off.

[Jeffvette]

Roger, it's supposed to be delivered tomorrow afternoon I believe.

[rogerzr1]

Roger, it's supposed to be delivered tomorrow afternoon I believe.

Thanks Jeff. I will let you know what happens when I hook it up. If it gets here tomorrow I will hook it up then. Thanks again for your help.

[Jeffvette]

No problem, hope to see you in Birmingham.

[rogerzr1]

No problem, hope to see you in Birmingham.

Looks like Birmingham isn't going to happen for me.:thumbsdo:

I changed the ECM and there was no change. I appreciate your help Jeff, I will send the ECM back tomorrow.

With the ECM elimenated as the problem, looks like I will be going under the plenum for some answers.

What is my next step. I had new plugs put in in August, but I am not ruling that out. I have a set of spark plug cables to put on.

What gaskets do I need to get before I start?
What other things like maybe a coil pack or what else?

Again my car stumbles at low rpms. It has been driving better at WOT since I replaced the o2 sensors, but occasionally stumbles there as well.

If I don't figure this thing out before summer I will video the explosion.
(anyone found me a stick of dynamite yet):wink:

[Demps]

What are the plugs gapped at?

[Polo-1]

did you ever check the TPS ?

Does it have a smooth sweep up and down in volts?

[XfireZ51]

Roger,

Have you ever checked the fuel pump clamps like SGS suggested? Lgaff had a similar issue which was remedied by stainless hose clamps.
Or you keep talking about ambient temps affecting the performance.
Have you tried looking at the Coolant Temp Sensor and replacing?
The hesitation sounds like its going lean at tip in and for AE.
Again, a scantool would REALLY help here and save time/effort.

[rogerzr1]

I talked withy Jeff and looks like I will hopefully get him to look at the car while he is in Birmingham. As I told him, I have never worked on cars before. Looks like I picked a good vehicle to start with.:o

Hopefully I will have some good news after next weekend.

I appreciate everyones help!!! :worship:

Seems like everyone on the Registry is willing to help a brother of the beast out.

I am hoping soon to not be sooooo much trouble.

[blackjack]

sounds like bad spark plug to me
bj
91/1735

[rogerzr1]

sounds like bad spark plug to me
bj
91/1735

I sure hope it is something that simple.

[blackjack]

happened to me(not with the z)....your favorite mechanic drops a plug on the floor,and still puts it in[-X
bj

[Demps]

One more try...what are the plugs gapped at?

[rogerzr1]

One more try...what are the plugs gapped at?

I am sad to say I don't know. They are the Ac Delco plugs. The mechanic that put the in said they were the correct ones for the car, but right now that doesn't mean much to me.

Hope to find some answers next Friday.

[blackjack]

gm recommends .035'' for 90-92,and .050'' for 93-95...generally speaking,a smaller gap will give you easier starting while a wider gap is better for high speed...i would start with .035'',and go from there,keeping in mind that too wide a gap can cause misfiring,,,mine are set at .040''
91/1735

[Pete]

Spark plugs are a cheap place to start.

I had a bad spark plug on the Z loosing pressure.
I started with the cheapest parts spark plugs.

And make sure you gap then .032- .035 i don't care what GM reccommands.

Pete

[karterdon]

One quick thing to look at - The vacuum hoses on the back of the plennum and on the fuel pressure regulator. If you had a slight back fire - they may have come off. Might contribute to your fuel issue.

Good Luck

D.Y. 91-#267
:)

[rogerzr1]

Issue resolved!!!!!

ALL HAIL JEFFVETTE.:worship: :worship: :worship: :worship: :worship:

I went to Birmingham to the vette gathering. Jeff was there helping Fred with his Zo6 race car and for the vette get together. After a long day driving the Zo6 on the track, Jeff took a couple of hours to help me with my car(I know he was tired). We were at Chris's house. (aka. Corvette95-Talk about a garage and car room. I hope Chris will post some pics of his garage, paint shop, basement room, and attick. Amazing). He was nice enough to allow us the use of his great garage. Anyway, long story short, problem turned out to be coil packs. Once again Jeff had anticipated this and brought the materials needed.

I have had the car since August 2007. Last night on my way home is the first time the car drove like it was supposed to drive. Man what a feeling!!!:D

I took a number of photos at the race track where Fred Turner and Jeff were taking turns in the zo6. I will post some when I figure out how to do it.

Again let me thank everyone for their input and help.

Jeff you are the man!!!!!

[Hammer]

Outstanding. I assume you will not be giving your car away now. LOL.
Congrats.

[rogerzr1]

Outstanding. I assume you will not be giving your car away now. LOL.
Congrats.

Not going to blow her up now.:D

Now just looking forward to some more things I can do to the car, when I can afford it.

BTW. When I got my car it had a ground effects kit and wing(still does). You could tell Jeff was envious of my wing.:wink:

[bradslt5]

glad the problem is fixed roger . no one has worked harder than you to try to find out what it was . it sure was nice of jeff to help you out . just goes to show what a great bunch of guy lurk here doing what ever they can to help those in need . sometimes it takes a person with jeff knowledge to fix our cars . he could fix them in his sleep i think. did ya buy him a pizza ? car is fun now huh?

[rogerzr1]

glad the problem is fixed roger . no one has worked harder than you to try to find out what it was . it sure was nice of jeff to help you out . just goes to show what a great bunch of guy lurk here doing what ever they can to help those in need . sometimes it takes a person with jeff knowledge to fix our cars . he could fix them in his sleep i think. did ya buy him a pizza ? car is fun now huh?

Yes, the car is a lot of fun now.

Jeff seemed to be more into Philly cheese steak than pizza.

Hope all is well with you and Deb.

[Jeffvette]

Roger, it was a pleasure meeting you and having you hang out for a bit. Fred really enjoyed giving you a ride at the track at speed and getting a feel for the track going. I think that high was only surpassed when you drove your car after the coil pack change.

Hope to see you at Petit in October.


Chris, thanks for the use of your garage and tools.

[fhturner]

Great to meet you, Roger (and Chris as well!). I cannot think of a more enjoyable weekend that I've had in a long time. I'm so happy for you that your Z is running as it should now! But we can't forget your quote after you took it out for a test drive once Jeff fixed you up: "Is it wrong to love another man?!?!" LOL! That made it all worthwhile, buddy! :D

BTW, I sure wish you could have stuck around to ride for a few more laps today. I know you had such a blast yesterday, (and it really made my weekend to hear you so excited about it!) but we just got goin yesterday when the checkered waved-- we weren't even up to speed yet! We'll have to reschedule you for another run sometime... Anyway, glad you can enjoy your Z now....good luck w/ the wing and ground effects! :D

Fred

[bradslt5]

wow roger , 2 e ticket rides in one day , sounds like you had an awsome day .its nice to see a group of folk care so much .now if we could have that rub off on the world ..... oh well just a thought . i would have been scared to death in that race car. i can only do straight line .so auto crossing in your future ?those rides can get ya hooked:)

[rogerzr1]

i would have been scared to death in that race car.


I wasn't scared.:jawdrop:

Who am I kidding heck yes I was scared in that race car.:o Like Fred said the tires hadn't gotten a chance to even heat up and I was screaming like a girl. There is one turn where you come over a hill moving right, I don't know how fast we were going, all I know is we were moving laterally as well as forward and Fred never got off of the gas. This was the turn where a guy dumped his Porche turbo.

It was great. Way too expensive a hoby for me right now though.

Fred gave me a new appreciation for REAL driving.:worship:

I hate I had to end my weekend short late on Saturday.(sick kid at home)

I look foreward to anymore events that gets guys like this together.

Man it was fun.:D

[Lowflight]

I read this whole freakin thread and the guy with the problem never told us what it was[-X

[HIZNHRZ]

The problem was clearly the exhaust I sold him.:D

[bradslt5]

oh yes it does . go fish:mrgreen: got any coils

[Jeffvette]

I read this whole freakin thread and the guy with the problem never told us what it was[-X

Weak coils.