Guys, I'm bumping this again.


A few months ago I was at 350 miles of reliability - it's just a weekend warrior car. When, driving to work on flat ground, for no apparent reason, the car stalled.


Used to, I had these issues of it running poorly, stumbling, back firing, loading up, randomly stalling, etc.

Now it is simply like someone turned the key off while driving. MOST of the time, I pull over and it'll fire right back up. But sometimes it takes 20+ minutes of sitting. Also, if I pop the hood w/ the key in the ON position and reach back and jiggle the main harness over the heater box area I get some relays clicking and I can hear to fuel pump prime. Usually then I can start it, but sometimes not.

It's been suggested to me that while running I should jiggle the keys/ignition switch and if it stalls, that's my culprit. Well, I've done that and the car doesn't stall.


I'm really thinking of opening up the ECU (is this safe?) and seeing if something is inside there loose or floating around making contact every now and then and shutting the car off.

I don't know WTF else to do.



Is there was a way to diagnose this issue!?


I just feel like I'm at the mercy of the car. This is really getting old and the car is just sitting for year after year.

 

Anyone have a source for a wiring harness for '94 Z28 M6?

Do I need a shop to sync up a new ECU if I try a remanufactured one?


Can a good shop data-log while I drive and thus diagnose the issue maybe? Only problem here is sometimes it happens very infrequently, like 200-300 miles apart, other times it happens 3 or 4 times a day.

 

If a wiring problem is shutting down the engine, it may cause a code to be set. I'd start by scanning for codes. It isn't going to set a code for a bad ignition switch, and that seems to be an increasing problem as these cars age. But if you are losing the signal from the Opti, or the signal to the ICM, or the ICM is breaking down due to heat soak, you should be getting a code. And not all codes turn on the SES light.

If you buy a new PCM, it's a good idea to have it set up with your VIN, and you have to insure the PCM has the correct programming for your specific vehicle/engine/trans. The fact that the existing PCM has a pcmforless sticker on it does not necessarily mean the PCM is "aftermarket"... could just mean that at some point in it's life it was sent to pcmforless for a tune.

 

I've owned the car 8+ years but I believe I was told it had a "mad Z28 tune" in it when I bought the car. It has full length headers w/o EGR, CAI, airfoil, etc. The simple stuff.

I have a brand new ICM and it has the "spacer nuts" under it to keep it off the head. I really don't think the ICM is having issues unless it's a wiring thing related to it.

At this point I'm ready to solder the opti harness directly into the harness on the passenger side of the intake.

Maybe I'll toss an ignition switch in it just for the hell of it. This is such an annoying issue!!

 

Bad ground strap on the stud that holds the ICM bracket could be a problem. Open circuit sets DTC 41 on cranking, and this code does not turn on the SES light.

 

I have previously cleaned some of the grounds (wire brush their contact point, bolt, washers, etc) around the front driver's side subframe and core support. I'll have to double check the one on the ICM studs.



Is my best bet to literally start the car and very meticulously, one-by-one, jiggle each and every wire/harness/connector?



I was thinking of opening up the PCM and checking for anything loose inside of it, is there any big danger in doing this?

 

Yeah, after replacing the ignition switch today at a friend's urging, I still have the same crazy intermittent problem.

Fuel pressure is 42 at key on, 36 while running. Blip throttle it raises to 41-42 then settles back at 36. When it dies, fuel pressure never goes away.

Also - when it dies if I have a CD playing - the whole CD starts back at song 1 - so it's a total power loss issue.

and... HOLY ****. I oped up the PCM and well.... here ya go....

http://s1215.photobucket.com/user/pr...?sort=3&page=1

Now, if I didn't know any better (I've owned the car 8+ years) I'd think this bitch sat at the bottom of a river for a few weeks.

Here's the catch - the car performed GREAT for 3 years. Then sat it a covered barn for 2+ years and has been sitting (infrequently driving) in my driveway another 4 years.

IDK how all that debris got in there!?

I used 2 cans of contact cleaner + q-tips with alcohol and cleaned everything very well. Put it all back together and the can is still very intermittent.




Where I'm at right now is back to running diagnostics on the Opti, and hoping that IS it actually. At least then I'll have a definitive answer.

This is un-freaking-real.

 

whining.

 

By the way, I pulled that ground strap while the car was running and it did nothing. Kept running just fine.

I unplugged the MAF while the car was running also - it stumbled a few times but didn't die.

So it would seem all that stuff is fine.