Engine Missing

[c4zr1]

I need a little help. I have a 92 with 17,200 miles on it. I know I do not drive it enough. It developed a miss and the engine service light is staying on. The secondaries are not coming on. I have changed out the plugs and fuel filter. Did not help. I am not getting any codes. The engine is idling right at 500rpm. I did do a reverse vacuum check and the vacuum does not hold constant, it leaks back down slow, but the vacuum pump does not stay on all of the time. It comes on about every 15 seconds and stays on for about 5 seconds. I did notice plug #1 and #8 was pretty black, but not wet with fuel.
I wish there was someone close that I could take it too, but Dallas is 6hrs away. Does anyone know of a good ZR-1 mechanic in Oklahoma City? I am only 4 hrs away from there.
Any help would be appreciated.

[Pete]

I think Jerry Downy lives in Oklahoma don't know where in Oklahoma he's at Carlilse this weekend try him on Monday.

Jerry is good people.

You can contact him at www.jerrysgaskets.com (http://www.jerrysgaskets.com)

I would say spark plug wires or bad injector.
Pete

[Paul Workman]

My engine is missing so bad...I can't even find it in the car!! :dontknow: (Just kiddin...sorta. Actually the engine IS missing from the car at the "moment" [sigh])

What Pete says is where I'd look first as well. But, if you have an SES situation, the secondaries will not be commanded open by the ECM. And, there should be a code too; at least while the SES light is on.

You can have it scanned at many of the auto parts stores; many do it for free. Scanners are great diagnostic tools, however they don't always point to the problem; but sometimes to the result of a problem.

For example, a leaking or stuck open injector will not throw a code or invoke an SES light - directly. However, if excessive fuel forces the O2 sensor out of range, the scanner will pick it up instantly, and if the condition is sustained, the ECM will finally light the SES light - as long as the ECM is operating in CLOSED LOOP configuration.

It sounds like you have a slow leak in the secondary system's vacuum circuit as well. That might be another item on you list, but not the one causing the miss - the scanner will shed some light on the path.

Like Pete said, my suspicions too lie with the injectors at this point, and since you changed plugs with no affect, then possibly wiring. Try pulling one plug at a time while it is idling and see if you can detect which "holes" are not firing and let us know.

Gotta run!

P.

[c4zr1]

Update on the miss

I put in a set of NGK Iridium IX plugs. Put in some Lucas Injector cleaner ran about 3/4 tank of gas through the engine.
I did decide to take it to the local chevy dealer to let them run an engine analysis on the engine. Had an appointment at 8:30 yesterday morning. I never did hear anything from them so I went back at 5p.m. and ask the service adviser if I could have an update on my car. He told me that they have not been able to look at it. That did not set too good with me I certainly did not want to leave it overnight so I told him I would just take the car. When I got back home and in my driveway the engine service light went out. It seem to be hitting on all 8 cylinders. I decided to take it out for a spin. It did pretty good, the secondaries started to kick in. When pulling up to a stop the engine service light did come on a couple of times, but after I set there a couple of minutes letting it idle a little faster the light would go back out. I made it back home then without the service engine light coming back on.
3 hours later
I started the Z no engine service light. Great!
I put the Marc Haibeck chip back in. The engine was already running bad when I purchased the chip from Marc. I took that chip out and put the stock chip back in while trying to dianose the engine miss. I was hoping that might cure my problem.
I took the Z for a test drive.
It drives like a ZR-1 should now. The chip makes it even run better.
I think I had dirty injectors and eventually the Lucas Injector Cleaner cleared up the injector or injectors that was not working.
I feeeeel a whole lot better now.

Thanks to those that responded!
Don

[Paul Workman]

Update on the miss

I put in a set of NGK Iridium IX plugs. Put in some Lucas Injector cleaner ran about 3/4 tank of gas through the engine.
I did decide to take it to the local chevy dealer to let them run an engine analysis on the engine. Had an appointment at 8:30 yesterday morning. I never did hear anything from them so I went back at 5p.m. and ask the service adviser if I could have an update on my car. He told me that they have not been able to look at it. That did not set too good with me I certainly did not want to leave it overnight so I told him I would just take the car. When I got back home and in my driveway the engine service light went out. It seem to be hitting on all 8 cylinders. I decided to take it out for a spin. It did pretty good, the secondaries started to kick in. When pulling up to a stop the engine service light did come on a couple of times, but after I set there a couple of minutes letting it idle a little faster the light would go back out. I made it back home then without the service engine light coming back on.
3 hours later
I started the Z no engine service light. Great!
I put the Marc Haibeck chip back in. The engine was already running bad when I purchased the chip from Marc. I took that chip out and put the stock chip back in while trying to dianose the engine miss. I was hoping that might cure my problem.
I took the Z for a test drive.
It drives like a ZR-1 should now. The chip makes it even run better.
I think I had dirty injectors and eventually the Lucas Injector Cleaner cleared up the injector or injectors that was not working.
I feeeeel a whole lot better now.

Thanks to those that responded!
Don

Ummmm....OK. A good WOT now and then does wonders too. But, I've had the same set of symptoms which turned out to be O2s. A free scan from AutoZone would tell us a lot.

Just a thought. Hope it continues to please!

P.

[c4zr1]

Well things have changed some. I took my car back out today and I and I am still getting an SES light on from time to time. It will start up sometimes with the light on and some when I start it the SES light is out. When the SES light comes on I can drive it for a few miles and the light may go off, but when I get to a stop light it will come back on.
Puzzled.
I went by the local Auto Zone and they said they only scannd vehicles 96 and above so I could not get the codes read.

[Pete]

I went by the local Auto Zone and they said they only scannd vehicles 96 and above so I could not get the codes read.


Do the old paper clip trick.

Ground A & B terminals (2 top right terminals) on the ALDL plug turn ignition key to on position and count the SES light flashes,each code will flash 3 times.

Pete

[LGAFF]

They should sell OBD 1 ADapters to check the SES.....I bought mine at Wal MArt, they are only around $20.

[tf95ZR1]

They should sell OBD 1 ADapters to check the SES.....I bought mine at Wal MArt, they are only around $20.

http://www.gordonkillebrew.com/pages/800740/index.htm

[c4zr1]

Here are the codes I think I got when I did the A B pin cross
Code #34: Manifold Absolute Pressure Sensor Circuit Low - High Vacuum.
Code #42: Electronic Spark Timing (EST) Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #54: Fuel Pump Circuit (Low Voltage)
Here are the codes I think I got when I did the A G pin cross
1. C12 9. H72

Where do I go from here?

[tomtom72]

Here are the codes I think I got when I did the A B pin cross
Code #34: Manifold Absolute Pressure Sensor Circuit Low - High Vacuum.
Code #42: Electronic Spark Timing (EST) Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #54: Fuel Pump Circuit (Low Voltage)
Here are the codes I think I got when I did the A G pin cross
1. C12 9. H72

Where do I go from here?

Hi, I thought I would try to share some thoughts.

1. the EST code could be from a PROM ( MEMCAL ) not seated fully. You swapped chips & it might be worth a look. Unless some one disconned the DIS box connector and going back on they had it upside down. That will bend a pin on the box and give a 42...ask me how I know that one!:o

2. MAP low volts/high vac. Take a look and see if the MAP hose has oil in it, even the MAP itself can get oil into it and if it does it will simulate high engine vacuum. Our motors pass a bit of oil vapor from the PCV system into the plenum and then it can get into the MAP hose and sensor. Also, the MAP hose can get soft and collapse under engine vacuum and give the same code.

I would, after checking the MAP & hose and the PROM seating, disconnect the battery for a minute or two to clear the codes and start her up and see what there is to be seen. Not trying to be a wise guy. It's just sometimes multiple codes throw me for a loop till I remember to start with the lowest number code. Stupid Q: do you have a FSM? FWIW, two tools that I rely upon with this car are my scanner & software pkg and my FSM. Best money I spent besides Marc's chip!:thumbsup:

A senior member ( Jerry, our VP ) told us when you get multiple codes that don't seem to be related start with the lowest number code for the diagnostic procedure.

:cheers:
Tom

[c4zr1]

Tom,

Where is the DIS box connector? I am new at diagnostic stuff on my car. I do not know what all of your lingo means. I have not had any trouble with it since I have had it. I think it is from lack of driving it. I am going to start driving it more.
I do not have a FSM? FWIW, scanner & software pkg.
Tell me more where is the best place to get these things?
I will start with your advice. I have looked at the hose to the MAP and it has not come off. I think it has a small zip tie on it. I have not looked to see if it has oil inside of it. I will also check the prom again.

Thanks!
Don

[tomtom72]

Hi Don:hello:

Okay sorry for the "lingo":o

FSM = Factory Service Manual, it's a set of three books, or at least it was when I bought mine. Try this link:http://www.helminc.com/helm/homepage.asp?r=
These guys do GM's printing so they have the real stuff. Try to stay away from the Motors or Chilltons versions as they leave stuff out sometimes.

You will eventually need a scanner. I bought mine used on e-bay. The important thing is that you have to get the right software with any scanner or else it can't talk to your car.

MAP hose with a zip tie is not such a good thing. Our MAP hoses are supposed to be blown off in the event of a misfire when a start attempt is performed. Usually our LT5's back fire if we don't hold the key over in "start" position long enough for the motor to actually run. If you let off too soon it will back fire. The hose blows off to save the MAP sensor from damage. The zip tie on yours makes me suspect that the hose maybe oil soaked or soft or both. The OEM hose is made up from a hard small plastic bent line section that has two preformed rubber connector ends. The MAP hose can actually be taken apart into it's three pieces, plastic hose & two rubber ends.

Okay, so none of this trouble with you seeing any trouble codes & an SES light started till recently, after a long sleep? Just another fwiw, our electronics package is a power hog. If the battery has weak cell or cells it sometimes drives the ECM crazy....usually it wont start or crank but there is the odd chance that low cells upset the ECM. I bring my battery back every 3 to 4 yrs & it always tests "marginal" so I get a warr replacement. Sorry for all this stuff. I'm trying to think & write fast so you will not think we are leaving you flat!

Check the chip ( PROM ) and take a good look at the MAP hose for softness and or oil fouling. Let's start there..oh, forgot after you check that stuff do the disconn on the negative cable to clear the codes. Drive her and see what happens with the SES light. If it comes back then pull the codes and let us all know what is there this time around.

:cheers:
Tom

Don, sorry I forgot to answer the Q about the DIS connector. You really can't see it as the DIS box is bolted to the underside of the plenum at the rear. If you take the MAP sensor & bracket off and look up under the rear of the plenum you will just see it, actually you will see the connector a 12 wire son of a B. If no one has had the plenum off then dismiss that because they rarely fail.

[tomtom72]

Tom: I always enjoy watching you think on line....you are superb in diagnosis and explaining things (especially when it comes to codes).......there is another codes issue accuring at this time also http://www.zr1.net/forum/showthread.php?t=12754

Which I am thinking there is a simple solution since ALL codes are showing at the same time.....;)

I am learning ...and thank you :thumbsup:

Cliff, I need a brain to think with....my SES light is telling me that there is no ECM in the system!:sign10:

Straight up, thank you for the kudos. :o My problem is that I can't type as quickly as I think, and sometimes I can't think too quickly either! Senility, that's my story and I'm sticking to it!!;)

[c4zr1]

I checked the pins on my prom. All is good and straight.
I disconnected the battery to try and clear the codes.
I am still getting codes 42, 43, 44, and 54.
I have not take the MAP hose off yet.
That is my next step. It is zip tied. Sort of hard to get too.
I did take the top plate off above the MAP. Is it easier to take the torqe bolts out of the braket holding it to the plenum?

[tomtom72]

Okay Don, I smell a rat somewhere. It deleted one code and added one code.

I'll have to look over all the diagnostic trees in my FSM to see what I come up with.

The MAP bracket to plenum bolts are a bit of a bitach to r&r. Be careful or you will drop them onto the top of the transmission ( trust me done that one:o ).

I'll have to run down 42 in the "intermittents" section B of the FSM.
:cheers:
Tom

[c4zr1]

I did get the zip ties cut off of both ends of the rubber elbow of the MAP hose coming frm the plenum. It does look like a little oil residue in that elbow.

[tomtom72]

Okay, I don't like this. All these codes have one thing in common, faulty ECM, DIS, ESC.....bad grounds or shorted wiring, bad ECM plug terminals.

Humor me for a minute Don, also please don't be insulted either.

Your chip is from Marc Haibeck? Which kind did you get, a replacement PROM or the "piggy back" that you must insert into the backside of the PROM? If the latter, recheck your work on the install because the piggy back one must leave the first 13 slots open as they are the cylinder ID's, and obviously the PROM must be seated and the levers locked.


The last time something like this happened to one of our members it was the holes on the big plugs that go into the ECM, the holes opened up some how and made for some weird goings on! Search user name "tccrab". I'm just shooting in the dark at this point.

The only other thing all these codes have in common is bad wiring, lost grounds or shorts. Okay, so I left out that the DIS box failed, ECM failed, ESC module failed....you see where this is going, right? The car would not run in MHO if all that stuff was bad at once. This is proly something stupid.

btw, a scanner is of no help with 42. A test light and a digital VOM are the weapons of choice here. 43 you scan for knocks, 54 is bad relays besides wiring issues.

:cheers:
tom

[tomtom72]

I did get the zip ties cut off of both ends of the rubber elbow of the MAP hose coming frm the plenum. It does look like a little oil residue in that elbow.

Okay clean that stuff up well and see if any oil made it to the MAP sensor. I use a tissue rolled up to go into the hose port. Make sure the hose part is not at all soft because these motors create quite a vacuum. At idle an LT5 will suck in a hard cover loose leaf binder! Serious, it will actually break the cardboard covers from the suction thru the T/Body.

I still don't like what's going on with all these other codes. Let's do this one step at a time though.

:cheers:
Tom

[c4zr1]

I cleaned the MAP hose and MAP tube, put it back together.
I disconnected the battery for a few minutes hoping to clear the codes.
Took the car out for a spin. SES light was on when I started it. The LTPW light does come on from time to time. Will this code keep the secondaries from coming on?
SES light never went out when I was driving it.
It does seem to be running on all 8 cylinders, but not opening up the secondaries.
Pulled into the garage and read the cods again.
Still getting 42, 43, 44, and 54
I cannot seem to be able to clear the codes by disconnecting the battery.

[tomtom72]

Don, it looks to me that it is possible that there are actually two issues.:mad:

And, Yes if there is an SES light the secondaries are canceled till repairs are made. Anything to do with fuel, oil psi, coolant temps, ignition boxes, and a vacuum failure in the secondary port throttle system results in no secondaries usually.

I don't mean to be out of line here, but we have to settle on what exactly we are dealing with; as I see it there are two separate issues: ignition system issues and a fuel issue/O2 issue.

One easy ( maybe not exactly correct if you are a real Tech ) check is to swap a known good ECM into your car. If the codes come back then there must be something with the ignition and fuel pump. I'd do that because I'm some knuckle head back yard type!:o You don't have a spare ECM?

The fuel pump relay could be gone, ckt 120 open or shorted to ground, ckt 2 open,open or short in ckt 490, you get the idea. I only ran down about one half of one side of a two sided diagnostic tree under 54. You can guess that the other codes have similar diagnostic trees.

You could check all the grounds at the bell housing and any other grounds you can find for good connections. The rest is very difficult to do over the forum in real time. I'm not throwing you under the bus, but I don't have a scanner that I could use to e-mail you the FSM pages.

Tom

[c4zr1]

I decided to take the Z out to see if anything changed. I disconnected the battery for about 5 minutes hoping to clear the codes. It did not. When I started the car the SES light was on. I drove about 4 miles with the SES light on. Pulled up to a stop sign and the SES light went off. I took off and the car was running very good. It was hitting on all cylinders and the secondaries were kicking in.
I am beyond my testing ability. Should I start replacing parts? I am still getting several codes. 42, 43, 44, and 54. My next step is to get it to a shop I guess.

[gbrtng]

Don:

I had a similar problem with wifey's 91 L98. Several unrelated codes and intermittent. Turned out to be a bad ECM which I replaced and all OK for many moons. Put out an APB for a loaner replacement you can try out rather than throwing parts at it.

[tomtom72]

I decided to take the Z out to see if anything changed. I disconnected the battery for about 5 minutes hoping to clear the codes. It did not. When I started the car the SES light was on. I drove about 4 miles with the SES light on. Pulled up to a stop sign and the SES light went off. I took off and the car was running very good. It was hitting on all cylinders and the secondaries were kicking in.
I am beyond my testing ability. Should I start replacing parts? I am still getting several codes. 42, 43, 44, and 54. My next step is to get it to a shop I guess.

Don, No, emphatically NO. The last thing to start doing is throwing parts at it. It isn't cost effective with these computer cars.

Do you know anyone that has an ECM that is a "known good unit" that you can hit up for a loaner?

If not let me know as I have one in my parts inventory. I just do not have any EPROMs for other model year cars as mine is a 90.:mrgreen:

:cheers:
Tom

[XfireZ51]

A code 34 says the MAP voltage is too low at anything below 700rpm which is why he's getting SES at startup. I would replace MAP sensor or test the one you have with a DVM and Mity Vac. Having a scan too would be nice. If the MAP is reading incorrectly, it could cause the lean condition and affect correct timing. Also a code 42 says the ECM isn't doing the "handshake" with the DIS module and taking over timing after 400rpm. Could be using bypass mode.
Start with the MAP sensor.
As for the ECM, if you turn ignition to ON and get the SES blink, that's the ECM self test indicating ECM is good. If it stays on and no blink I would suspect prom first, then ECM.

[tomtom72]

Don, listen to Dominic ( XfireZ51 ) Trust me on this. I know that when there are many voices talking at you it gets a bit overwhelming. Trust me, listen to Dominic....if I knew what he forgot about the electronics on these cars, I'd be a top Tech!

Dominic, thanks for bringing your knowledge to this thread!:thumbsup:

:cheers:
Tom

[XfireZ51]

Don, listen to Dominic ( XfireZ51 ) Trust me on this. I know that when there are many voices talking at you it gets a bit overwhelming. Trust me, listen to Dominic....if I knew what he forgot about the electronics on these cars, I'd be a top Tech!

Dominic, thanks for bringing your knowledge to this thread!:thumbsup:

:cheers:
Tom

Tom,

Just adding my $.02. There are several other members here with much more experience than I. I appreciate the confidence and I hope this helps.

[c4zr1]

Tom,

I took your advice. I had a freind that has a 91 ZR-1 so I asked him if I could borrow his ECM. I put my prom in his ECM and did a swap.
No codes. I think I found the problem. Bad ECM.
Where is the best place to buy a ECM?

Thanks for everyone help.
Don

[XfireZ51]

Tom,

I took your advice. I had a freind that has a 91 ZR-1 so I asked him if I could borrow his ECM. I put my prom in his ECM and did a swap.
No codes. I think I found the problem. Bad ECM.
Where is the best place to buy a ECM?

Thanks for everyone help.
Don

Swap the prom back into the old ECM one more time to double check or use another prom.

[Kb7tif]

Swap the prom back into the old ECM one more time to double check or use another prom.

Yes double check old pcm, might of had a unseated/dirty connection on one of the 4 main connectors!! Hope thats all it was

[c4zr1]

I swaped back out the proms again and did not help. SES light is still on at startup.
I may send my ECM to Tom Henry and have them send back to GM for remanufacturing. 30 day process.

Don

[c4zr1]

:hello:Well after several months of waiting to find a ECM a kind ZR-1 member finally helped me out. Scott Collier sold me the one he had just bought off of ebay. Thanks Again Scott!
It was a 91 ECM. I put the Marc Haibeck PROM in it and put it in my 92.
Initial start up no SES light. Power Key was on like it should be with the PROM from Mark.
The car ran great. I took it for about a 20 mile drive. Now I know why I bought the ZR-1. They are really fun cars to drive. I did blow the cob webbs out of the engine.
Now I plan on sending my ECM off to get rebuilt.
Thanks Too All that helped.
Don

[Paul Workman]

Now I plan on sending my ECM off to get rebuilt.

Don

I just recently read something written by Marc Haibeck (maybe on his web site?) that he has a source to get the ECMs rebuilt. Not shilling for the guy here, but FYI - just another source for ECM repair to tuck away, just in case.

P.

[ScottZ95ZR1]

:hello:Well after several months of waiting to find a ECM a kind ZR-1 member finally helped me out. Scott Collier sold me the one he had just bought off of ebay. Thanks Again Scott!
It was a 91 ECM. I put the Marc Haibeck PROM in it and put it in my 92.
Initial start up no SES light. Power Key was on like it should be with the PROM from Mark.
The car ran great. I took it for about a 20 mile drive. Now I know why I bought the ZR-1. They are really fun cars to drive. I did blow the cob webbs out of the engine.
Now I plan on sending my ECM off to get rebuilt.
Thanks Too All that helped.
Don

Glad to hear the ECM worked for you and your beast is finally fixed. :cheers: