New Owner with Q's

[emmvette]

Hi, As mentioned in my other thread, I finally brought a 90 ZR-1 home.
Now its time to dig into a few issues and get her ready for some action.

It has 22k on the clock. Has not be run too much the last few years, but has been driven a few times a year to keep it up.

I have only driven it a little and I'm getting a few questions already.

The first is, I was told the car has the standard rear end gearing (3.45). In first gear at 7,000 rpm I'm hitting about 55 mph, second gear at 7,000 rpm is about 82 mph. Does this sound correct? Tires are OEM size. I think this is about correct, but not sure.

Second question is I'm getting some hesitation in a couple areas; the car will occasionally act like its really kicking in and surge. It is not doing this consistently, but occasionally. Its almost like a hard downshift or a very slight pause then it kicks in when the pedal is mashed. I noticed this about 3,000 rpm a few times - it doesn't consistently do that.
Car just had new plug and wires installed prior to my purchasing it.

Last question for today is the car seems to stumble a little around 6500-6,800 rpm. Almost like its missing or trying a little to backfire.

Any suggestions on where to start trouble shooting would be great. Hopefully basic stuff. I'm not afraid to turn a wrench, but will be learning as I go.

Oil is draining from the first oil change as I write.... drip, drip, drip.

[USAFPILOT]

gearing, yes, same as my 94. your secondary system could be acting up causing the surge, stumble.

[A26B]

Hi, As mentioned in my other thread, I finally brought a 90 ZR-1 home.
Now its time to dig into a few issues and get her ready for some action.

It has 22k on the clock. Has not be run too much the last few years, but has been driven a few times a year to keep it up.

I have only driven it a little and I'm getting a few questions already.

The first is, I was told the car has the standard rear end gearing (3.45). In first gear at 7,000 rpm I'm hitting about 55 mph, second gear at 7,000 rpm is about 82 mph. Does this sound correct? Tires are OEM size. I think this is about correct, but not sure.

Second question is I'm getting some hesitation in a couple areas; the car will occasionally act like its really kicking in and surge. It is not doing this consistently, but occasionally. Its almost like a hard downshift or a very slight pause then it kicks in when the pedal is mashed. I noticed this about 3,000 rpm a few times - it doesn't consistently do that.
Car just had new plug and wires installed prior to my purchasing it.

Last question for today is the car seems to stumble a little around 6500-6,800 rpm. Almost like its missing or trying a little to backfire.

Any suggestions on where to start trouble shooting would be great. Hopefully basic stuff. I'm not afraid to turn a wrench, but will be learning as I go.

Oil is draining from the first oil change as I write.... drip, drip, drip.


WELCOME!!

The vast majority of performance issues, much like the symptoms you described, are related to the following, in no particular order.

1. ignition: plugs, wires & coils
2. fuel: faulty fuel injectors (90~92 most common) and weak/bad fuel pumps
3. secondary port throttle system: vacuum leaks, bad vacuum check valves, faulty secondary solenoid valve.

[emmvette]

Thanks, I traced the vacuum line from the point to where it first breaks (next to the oil filter) and found the line pulled out of the rubber hose connector. When I cap it with my finger the pump stops, so it is fine.

When I put the hose back into the fitting the pump doesn't constantly run, it cycles continuously in 1-2 second intervals, so it would seem there is a fairly bad leak somewhere. I used a test vacuum pump / gauge at the fitting and it leaks down from 12/15" Hg to zero in under 2 seconds.
I've looked at the lines but they all disapear fairly quickly - it looks like it goes into the front center under the plenum. Do I need to pull the plenum to investigate ths further, or is there a better way? If I do this, I assume I need to get a plenum gasket first, is that correct? Is there anything else I want to be prepared to do while I'm in there?

I'll order service manuals Monday, but for now and going to have to do without. I found a vac line diagram in another post.



Thanks again.

[John Boothby]

Welcome to the asylum! First, you didn't say if you had any codes showing? This could answer some of your questions.

I would guess that your probs are most likely the secondary vac system. My suggestion would be to either completely rebuild the secondary vac system (under the plenum) no big deal, or remove it completely (secondary vac system). There are plenty of threads on this forum discussing how to do either one of these. The reason I say this is that you can spend a lot of time replacing bits and pieces (chasing the problem) or do it once and be done with it.

Also, if you have original injectors, they may have issues.

Good luck and have fun!!

[emmvette]

you didn't say if you had any codes showing? This could answer some of your questions.

***Honestly, my experience is with older cars ('68 vette), I don't know how to check for codes - would it tell me on the dash if there were a code to read?
I do have an idiot light on; its for the airbag, which was just fixed before I bought the car and it went back on again. My seatbelt light is also on, even though my belt is fastened. ***

I would guess that your probs are most likely the secondary vac system. My suggestion would be to either completely rebuild the secondary vac system (under the plenum) no big deal, or remove it completely (secondary vac system). There are plenty of threads on this forum discussing how to do either one of these. The reason I say this is that you can spend a lot of time replacing bits and pieces (chasing the problem) or do it once and be done with it.

*** After hooking up the loose vac connection I found by the oil filter, it no longer misses at high rpms, and is not "jerky" when I mash it So that is good, but it still leaks, so I'll plan to pull the plenum as you mention above.***

Also, if you have original injectors, they may have issues.

***Not sure if I do or not. The previous owner was unsure as he did not perform his own service and did not have complete repair receipts***


Good luck and have fun!!

Definately having fun! This car is a blast to drive.

Now for my new question of the day; when I shift at 7,000 rpm I can smell burnt fluid; I'm unsure if it is clutch, oil, or trans. I'll change the trans fluid in the next couple days - bought the Castrol 10W-60 liquid gold today.

[John Boothby]

Codes can be checked by grounding the "k" pin on the ALDL (third pin from right on bottom row), usually grounded to the seat frame. Turn ignition on (do not start). Read codes on the DIC. The warning lights will flash the codes.

Your "Infl Rest" light is probably indicative of a bad ground between one of the SIR sensors and the frame. There is a threat on this forum to correct this, and to clear codes. The seat belt light is tied to this circuit also.

I would highly recommend that you pick up the service manuals for your car. While they are not perfect, they do help alot. Also there are tech articles on this website that describe how to fix most of the problems that you have described. Check them out.

[batchman]

Definately having fun! This car is a blast to drive.

Now for my new question of the day; when I shift at 7,000 rpm I can smell burnt fluid; I'm unsure if it is clutch, oil, or trans. I'll change the trans fluid in the next couple days - bought the Castrol 10W-60 liquid gold today.

Smells after redline activity sound like PCV issues, probably some pooling happening on the intake and getting flung around. I run the tach up a lot and I know I need a catch can.

I would change the coolant also, especially if it sat a lot.

Cheers,
- Jeff

[We Gone]

Also you may want to check your clutch fluid, if the slave cylinder leaks it may be dripping on the cat or header driver side.

[Hammer]

Pull the hose in the middle of the plenum on the outside at about the middle on the drivers side with the car running. The pump should run continuously. Plug the end of the hose and if the secondary pump stops, the culprit is more than likely a little check valve on the secondary hose under there. I believe they are still available at the dealers. Part number 460734.

Another item to replace if you go under the plenum is the secondary vacuum tank, it is probably the biggest cause of the check valve not working correctly. That’s available from NAPA, Part #21013, it's only about $10.

Get some gaskets from Jerry and the parts above and I'll bet your problems are over.

[scottfab]

Yes indeed welcome to the party. Lots to learn.

One way to learn bunches is to use the "search" feature of the forum.
Go to the Technical section for instance and search for "clear codes".
Read up. You might also try "read codes". There is a cumbersome but effective way to do it with just a shorting strap(wire). Or you can buy that appropriate scanner to do it for you.

How does she run with the power key off? No need to trouble shoot the secondary system if you've got issues when they are not engaged.
If all runs fine with the power key off then assume, as has been mentioned, fuel pump and/or injectors and/or vacuum leak issues.
The leak you've described does sound like the check valve.
If you're going to pull the plenum consider cutting some gaskets yourself out of rubber. They can be used over and over without coming apart. Regular inner tube rubber works but you can find large sheets of the stuff on line. When the plenum is off you can use it as a guide for cutting the new gaskets.

One thing at a time. I'd suggest a separate thread per issue. It's not only easier to focus on the task at hand but can also be reused/found in searches by future forum users.

[Hammer]

Pull the hose in the middle of the plenum on the outside at about the middle on the drivers side with the car running. The pump should run continuously. Plug the end of the hose and if the secondary pump stops, the culprit is more than likely a little check valve on the secondary hose under there. I believe they are still available at the dealers. Part number 460734.

Another item to replace if you go under the plenum is the secondary vacuum tank, it is probably the biggest cause of the check valve not working correctly. That’s available from NAPA, Part #21013, it's only about $10.

Get some gaskets from Jerry and the parts above and I'll bet your problems are over.

I was actually wrong about the pump running all the tie when you pull the hose. It will be the same as when the car is normally running or not running. Just turn the key on, don't have to start it. If the pump is cycling as you mentioned, plug the hose, if it stops, then the check valve IS the culprit.

[XfireZ51]

Smells after redline activity sound like PCV issues, probably some pooling happening on the intake and getting flung around. I run the tach up a lot and I know I need a catch can.

I would change the coolant also, especially if it sat a lot.

Cheers,
- Jeff

Agreed. Burnt oil smell after WOT runs sounds like crankcase pressurization. Check for oil leaks but the cause will be venting of crankcase or actually not venting crankcase.
So PCV first, if not, then cam cover vents.

[emmvette]

Ok, thanks for all the replys and suggestions. Hammer, I'll try the tip you mentioned tomorrow.

Regarding the smell, I have to admit what was determined.... a little embarassing.... it would help if I didn't slip the cluth at high rpms. That problem is solved!

Took it to the track, today. Wow, what a blast to drive! This car is awesome and can really pull. It really is a beast. At some point, I'll write up a comparison of how this car drives compared to my '04 Z06. They really are very different. Handling goes to the Z06, fun award goes to the ZR-1, and since I'm not trying to win an award on the track; I like the ZR-1!
Its funny, I had a decent amount of comments on it being a ZR-1 and a few people seems agast that I was willing to risk tearing up the ZR-1 on a track versus keeping it in my garage clean & safe. Other than the wheel bearings, this car seems to be very well put together and feels really solid on the track.

[XfireZ51]

The motor is bulletproof. You can't kill it accidentally. So u can drive the p*ss out of it. More so than an LSx. Something else will give out before the motor.