Received this via PM, bringing it to open discussion.

I wonder if possibly your A/C compressor seized. I also had a stumble issue when warm when I first got the car, but a seafoam treatment, air filter, fuel filter, plus spark plugs, seem to cure the issue. Also, I believe the computer controls pulse by grounding the injectors, and the quickest way to check for pulse is to take a 193/194 bulb, unplug the injector, and stick the wires in to the plug. That will tell you.

Thanks for making this thread, this problem has cost me nerve, and money, and I have yet to find the exact issue, I had a mechanic check the car out for me, he told me he could get it to run fine if he sprayed fuel into the throttle body.
And that he tested fuel pressure, and it was a little low, so he replaced the pump for me, and got the spec pressure back.
It still would not run, and he told me he thought the PCM had a bad injector circuit, but I had read the CKP could be the culprit, so I had him replace that, it still did not fix it, so I paid to get it towed back home, and have been careless for a few months, which sucks when you live 20 miles from town, or any stores..

I replaced my plugs recently, and did a compression test, I noticed my cylinder #3 had a lot more pressure, it was closer to what you think they should be which was 170, all of the others were 145 to 150, so I am assuming the difference I have in compression is from carbon build up on the piston maybe.

I will be replacing my wires soon, because two of then broke off at the boot when I pulled them from the back, so maybe the wires were already getting weak, and caused them to deliver less spark.

I cleaned off My MAF, and also cleaned off my IAC pintle, that thing was full of carbon.
I pulled my EGR and tested that pintle out a bit, it was full of carbon, and on occasion it would stick open, I worked at it a few more times and it quit sticking, so this may be what was causing my issues, since you do not want that EGR opening unless you are at WOT.
Of course I will not know till I get the car back together so I can properly test a few more things myself.


I discovered I had oil, and possibly transmission fluid all over a few parts up under my car, I have pics of my undercarriage leak/mess at a friends img hosting site, I could show you them if they become relevant to whatever may be the issue, I say this because for all I know the small transmission fluid leak I noticed a while back when topping off could have gotten fluid on my CMP, and maybe messed up its connector, but I've gotten no CMP codes...
I put some stop leak in and never seen the tiny leak spray up on the alternator belt & power steering pump fluid area again...
So maybe my leak was from my LIM gasket failing, it was disintegrated pretty much, it fell to pieces as I removed it...

Sorry, meant to post this in my previous post.

My AC was working fine when it ran, I had just refilled it myself, I made sure to not over-pressurize it.

If the AC Compressor failed would it cause my injector pulses to be disabled?
The car did did at idle as soon as I cut the AC on, right after I replaced the coil back for cylinder 3/6, since I had gotten a cylinder 3 misfire code before it died.

I still think maybe my injector(*) may have an issue, when I replaced my fuel filter, when fuel spilled out from it, a lot of it was really dark looking, almost black...

I should state that my car is a 96 Park Ave, Base Vin K, it has 133k miles, I have owned it since 28k, and it has always been pretty well taken care of, for the 100k I put on it I made sure it always had fresh mobile 1 synthetic in it, and always stayed on top of my fluid levels, flushes, etc...

Missed part of your post, sorry I have been up quite a while.

I cleaned my K&N air filter, and re-oiled it, making sure not to over-oil it, also replaced all plugs with AC Delco Iridium, the PCM does control the injector pulses, but I think that all has to pass through a few sensors, like the CMP, maybe the CKP, then the PCM gets the ok to fire the injectors.
My car does have a PassKey II security system, and the VATS type pellet in the key, but I have tested that system, bypassed the need for the pellet in the key, and tested the Theft Deterrent Module, as that can also cause the injectors not to get the signal to fire.

I replaced my PCM with a used one flashed for my vehicle, so I know my PCM is good, the mechanic told me the signal wire from the PCM to Injectors was good, he tested it for resistance..

I plan to get my own injector test kit soon, after I get the parts to but my IM back together, I'm sure my injectors are not pulsing though, as when it was together this is what my mechanic told me after testing them with a NOID light.

Last post for now, I promise, if you could merge all of these into one post it would be fine by me, I don't want the thread to be messy. :o

I forgot one last thing, I did replace the ICM also, and when the car is back together I will test all plugs for spark with my inline spark tester, I'm fairly sure it always had a good spark, because the mechanic said he tested it, but I want to test it myself to verify.

I know once I can get it t run I'll have do do a Case Learn on it, since the CKP was replaced, but one thing at a time..

I've been doing a little thinking, is it possible the LIM Gasket going bad, as well as the UIM Gasket partially bad have allowed enough un-metered air to enter the engine to cause it to not start on occasion, and eventually go totally dead somehow?

Or could the CMP Sensor go bad if fluid got on it, and cause injectors not to pulse?


Sorry about all the typos in my replies above, I noticed like five of them, also sorry for so many questions, being without a car for 4 months is tough. :o

theres alot of info there, i like to try to keep things simple. if you put your car together what is it doing? stalling when you turn on the a/c? is it completely dead? why do you think that the injectors are not firing?

Yea I know there is a lot of info, sorry about that.

Before I noticed I had oil leaking out of what appeared to be the LIM, it was totally dead, and it died while it was idling in my driveway, right after I had replaced the #3 coil pack because it was not sending a spark to #3, as soon as I replaced it the car ran fine till I made it home, I knew I had an issue before, where running the AC would cause it to die, so I wanted to see if it still did, so I turned the AC on while sitting.idling, and it totally died kind of like it stopped getting gas.
So I had it towed to a mechanic nearby, and while it was together he told me the injectors were not pulsing at all, and he thought it was the PCM, but as I said I have replaced the PCM already.

Now when I say totally dead, let me correct that, it was cranking, but would not run but for a second or two, on occasion before it became totally dead, when it did this I could pump the gas pedal, and that would occasionally clear it up, and it would run like normal again.
The start, run for 1-2 seconds and quit, is what had me thinking passkey system at first, but I am almost 100% positive that is fine, the only thing I have not tested in regards to it is the wire that normally has 5v, but reduces to 1.96-2.50v when the car is cranked, it functions properly at the TDM, so I know that fuel enable circuit part of the theft deterrent module is sending out a signal to the PCM, I never tested to see if it was sending that same voltage to where that blue wire terminates at the PCM, I plan to do that once I get it back together, if it still will not stay running.

I'll stop there, as I do not want to add much more to this, as I do not want to make it over complicated.

I do have a thread with a lot of pics of the LIM job I'm doing at another forum, but I'm not sure if posting links to other forums is ok here.

did your fuel pressure ever get checked? what is it key on engine off? does it stay?

The mechanic said he checked it, I do not remember exactly what PSI he said it was, I think he said like 34-35, he just told me that it was low, and he thought that was the problem, he said when he put in the cheap aftermarket pump it had the pressure it was supposed to, he did not tell me if he did a leak-down test or not.
Once I get it back together I have been considering getting an Actron CP7838 Professional Fuel Pressure Tester, and then testing to see if it keeps pressure.

I have had it in the ON position for a while, and then pressed in the schrader valve with a rag in front of it, and it shoots out at what seems to be a high pressure, of course I cannot guess if it is loosing pressure that way, so when I can I'll perform that test.
I did take my fuel pressure regulator out, and cleaned the screen off, and tried to blow through it, I quickly found that did no good, but I did notice that once I out it back, and re-pressurized the rail, it shot out of the schrader valve a lot harder..

I do have an issue with my fuel inlet line, the little yellow O Ring in it appears to have failed, I was told there were two of them, I could not find an innermost one however, I'm trying to replace those, if I can in fact find the other one that is supposed to be there, as it could have been causing an occasional fuel drop, I know from the looks of it it had leaked on and off for a while, whenever you'd tap the top of that inlet lightly it would spurt out fuel, the front line, which I think is the return line does not do that.

Does anybody here know where I can find the little yellowish O Rings that go to the fuel rail?
I ordered something I thought was them, GM Part# 19238128, but they are black, and way to big, I tried to get them from the dealer, but was told they could only sell me the whole fuel line as it was a fire risk if they just sold me the o rings...

I could cut it and splice it to AN, or so I was told, I'm not sure if that is necessary though, I'd rather spend a few bucks on 2two o rings then to spend a lot more splicing in another line, regardless I want it to be safe, as it is a fuel line.