JSkeet

From my other thread which doesn't seem to be getting much attention. This is a whole new can of worms so I figured a new thread is in order.

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Original thread:
https://www.camaroz28.com/forums/lt1...n-cold-869107/

Most recent post:
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. Oil pressure is steady while running, I believe when warm it was reading around 20, cold it was more like 40.

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.

I ran out of ideas so I opened up the PCM and well.... here ya go....

1994 Camaro Z28 M6 Photos by project1984 | Photobucket

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 while I chased down an opti problem which now seems to have never been an opti problem perhaps.

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 car 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.



Does anyone think this could be a failing oil pressure sensor or even oil pump? If I'm not mistaken, doesn't it have the "power" to kill the engine if it sees a sudden loss of pressure? If the oil pressure sensor is on the driver's side of the oil pan (or is that a temp sensor?) with 2 wires coming from it, mine is weeping a bit and could very well be bad.

Does this sound like it could be a bad battery ground wire?

Any help, ideas, suggestions, would be greatly appreciated. I've got well over 60+ hours trying to figure this goofy thing out and it's now like my life's mission to do so.

Thanks

JSkeet

FYI - the issue is now absolutely random while sitting in my driveway. Cold, hot, doesn't matter. Sometimes it will fire up and run for 2+ hours with no issues. Other times it'll fire up and run for 5 minutes and die. Sometimes when it dies it will restart immediately, other times it will just crank and/or stumble but not start. Sometimes 20 minutes later it will start, sometimes it won't.


Earlier this spring I thought it was a wiring issue because if I jerked around on the main wiring harness over the heater box/firewall I could hear some weird relay/solenoid noises being actuated. (this actually sounded like it was coming from the ABS distribution block - almost sounded like a coin bouncing around) I attributed that to a loose connection on the PCM from broken retainer tabs on one of the harnesses, I believe the red harness, I could have the color wrong.

I've since corrected that issue w/ a bracket + zip ties to secure the harness to the PCM.

Running out of ideas after the most recent ignition switch swap failed to correct the issue, I opened up the PCM to find what is in the photobucket link above.

The harnesses and pins for the PCM are all clean (I cleaned them w/ contact cleaner), unburnt, unbent, etc. The boards were horribly dirty with this white silt type debris so I cleaned them also w/ contact cleaner spray. The problem did not change at all.

At this point I'm really thinking it's either a bad PCM or bad Opti again. Someone suggested I try adding a new negative battery cable to a top mounted ground, so I'm going to do that ASAP.

When the car runs, it runs great. No stumbling or surging.


ICM is new delphi mounted on studs spaced off the head.

Opti is a delphi w/ maybe 600 total miles on it, been having problems since around 100 miles.

MAF is clean.

Coil checks out fine on ohm check.

Ground strap from ICM is secure and clean.

Coolant temp sensors are both new.

Fuel pressure 42 at prime, 36 running.

Oil pressure is 40 cold, 20 hot. (sometimes when cranking after it dies, I've noticed the oil pressure doesn't seem to climb while cranking)

The initial issue which caused all this was I missed a very high RPM 2nd gear shift and the car stalled immediately. Opti that came out had a nice rattle to it. Figured swapping the opti would be the cure, but since then the car has had zero reliability w/ this random issue.

Strick

This is interesting to me as I'm wiring a 95 LT1 into an 83 Camaro. I have been tracing every wire that comes out of the PCM to see if I need all of them. There are many sensor inputs to the PCM. My first suggestion would be to check all of the sensors and the wiring going to them. Next I would contact someone like PCM4less and ask a few questions.

Normally, when a GM PCM shuts down an engine it does it by shutting off the fuel pump or retarding the spark. Does your system have a rev limiter?

JSkeet

If there's a limiter in it, it's further up than the mechanicals can tolerate because when I missed 2nd gear I'm sure it was north of 7k and that's when the original Opti popped.

Although there are many sensor inputs to the PCM, to my knowledge, there are only a few that have the ability to shut down the engine.

From what I've watched while the car is idling the fuel pressure does not drop when the car dies.

It dies fast, just like you turned the key off. No stumble or bog, it just dies.

The few times it happened while I was driving the car I tried to clutch start it and it would almost start but wouldn't quite do it.

It has never back fired either. Even when it dies then lets me restart it right away. So I don't think it's dumping fuel when it dies.

Injuneer

The reason you aren't getting a lot of responses is because I seriously doubt there are many people here who have ever opened their PCM. I'd send the link to pcmforless, and ask their opinion... might answer, might not, but at least ask. I will also ask our LT1 PCM expert, GaryDoug to take a look at the photos.

Problem with starting all over is you've lost continuity with the previous posts, what you have done, etc. For example, even though I TRIED to help in your previous threads, I can't remember all the details. Did you scan it for codes? That would pin down a problem with the Opti cam position sensor signal rather definitively. If you get DTC 16, you have a problem. Other possible failure of the Opti is the rotor coming loose, but that is going to cause it to run rough, misfire, etc... not just shut down in an instant.

I also think a scan might be the way to go. Have you considered running Scan94/95.

The F-Body LT1 does not have an interlock between the oil pressure sensor and the PCM. I answered that in a previous thread.

The sensor on the oil pan is the oil level sensor. That also does not connect to the PCM.

Have you checked the coil wire for corrosion?

JSkeet

I really appreciate the help you have offered Injuneer.

The issue w/ running a scan/data record is simple - I don't own a laptop nor do I understand how all that stuff works. I'm a bit out of touch with tech, still own a flip phone in fact! (weird, I'm only 29 years old...)

At one point in the past I remember having to cut/repair one of the coil wires because it was kinked in a very tight way overtop the harness and I feared internal breakage. I think the wire insulation may have been open actually, from being kinked so hard.

That said, I have jiggled it dozens of times, along with about every wire under the hood individually, while the car is running, and nothing seems definitively the culprit.

I can jiggle all the wires I want and get zero response from the car. Stand back and scratch my head and the damn thing just shuts off.

I tired calling PCMforless from the telephone number I found on the sticker on the PCM but the number was disconnected, I assumed they closed up shop. I will try to reach them as you suggest.

Injuneer

I'm talking about the high voltage coil wire. They corrode and can cause the engine to shut down. But the fact your CD player resets is telling me this is a power supply problem.

pcmforless is still in business, and going strong:

Home | PCM for Less

It's really not fair to complain about a lack of response, when you appear unwilling to even try to find a way to scan the car. It's sort of like entering a prize fight with one hand tied behind your back.

JSkeet

Just found pcmforless.com and sent them the info/pics.

Will wait to hear back.

JSkeet

Sorry to appear unwilling. I'm not, I just kept assuming I had it fixed previous and later found out that I did not.

At this point, I'll buy the mecca of laptops and figure this all out to get data if absolutely need be.

Strick

I think it's cheaper to contact PCMforLess and let them work with it.

GaryDoug

Sorry I haven't read all the topic posts yet, but if you cleaned the pcm with ordinary drug store alcohol, that may not get the job done. You really need 100% pure alcohol, and get under the parts that are tight to the circuit board.. The rubbing alcohol type has water it and would short out things unless it was very thoroughly dried, and it really isn't that good for cleaning electronics assemblies.

Out of town right now and replying with the old laptop ;-)

JSkeet

Got an email back from PCMforless.com and just said basically, it's not a tune related issue, you need a new PCM, it will be $XXX for a new tuned PCM.



So, I'm contacting a guy on LS1tech.com about a possible solution to see his pricing.

I don't wanna shell out that kinda money and get no warranty.


GaryDoug - I used 2 cans of spray electrical contact cleaner then used just q-tips and 91% alcohol and the pin/harness attachment points to rub some fine dirt off there. I allowed everything to sit about an hour before putting it back together. It was all very clean and dry upon reassembly.

Strick

After following this thread, it seems to me that you are going to have to make a decision. Do you want to fix it or not. To fix the PCM will take $XXX and if you don't want to shell out that money, then sell the car. Warranties on these PCMs are not available except if you buy one from an auto parts store and it will probably be a rebuilt one. Then comes the tune if you are running something other than stock.

Thirim

drug store 99% isopropanol alcohol and a box of Q-tips.. it will do wonders.
From your pictures I would hazard to guess someone has cracked the seal on the PCM before or the seal failed and moisture got inside. The alcohol is a cheap try and quick. You may clean it up and the damage is done already but hey, $5 bottle of alcohol...
As for the CD player losing power after it quits, I don't see anything in the PCM wiring to suggest the memory wire on the stereo is connected to the PCM.
Maybe check pin B15 and B31 for battery voltage as you're waiting for the engine to die in the driveway. Crack open a Chilton manual or whatever to see if there is something related to either of those wires and your memory wire on your stereo?

Tex95Z

I had a similar issue on my 92 camaro. Would run great for awhile, then just randomly die. Wait a few minutes, run great, randomly die. I changed a lot of parts that were prone to shut off with heat. Turned out to be a internally corroded ground and power wire off the battery. Corroded right in the center of the wire. You should check yours.