I've posted on the general tech board, but haven't gotten much help so I'll try here.

I've got an '89 IROC L98 that is stumbling more and more. I've had some problems with her and replaced alot of stuff. When the engine is cold, there really isn't much problem except for a small idle hunt between 750 and 600 rpm. When it gets to operating temperature it stumbles all over the place at any rpm. It just recently began developing the stumble at higher rpm. I have put a new cap, coil, rotor, wires, and plugs on the car all from Accel. I do hear the rotor clicking against the cap contacts from time to time when I start the car. I've replaced the EGR valve, and tested my coolant temp sensor as well as adjusting my TPS. It really has not done much good. I don't have access to a scanner or laptop but the fuel mileage has been suffering lately as well. I checked my injectors about 2 weeks ago and got between 12 and 14.2 ohms for each. I can feel them clicking and believe they are working. The computer is throwing a code 36, and I have replaced everything in that circuit except for the ECM.

I've also had a problem with voltage. Again, while cold, the charge will be about 14V. The voltage will drop when it hits closed loop to about 13V while driving, and sometimes to 10V while stopped at a light in drive. If I put the car in neutral the voltage will increase slightly. This is all with a new 140 amp alternator.

I should add that I've set the base timing to 6* with the EST connector disconnected. Once the timing was set I reconnected the EST, and the computer advanced the timing beyond the timing marks.

What do you guys think is up with my car?

 

Hey I just noticed something. When I take the car out and it's cool outside, there is hardly any stumble at all. What are the chances my ignition module is getting too hot causing this? I did put dielectric grease between the module and distributor base, but maybe I didn't put enough? That is what I'm supposed to use isn't it? What else could it be?

 

Same problem I had - ignition module fixed it - I just got the cheap $30 autozone lifetime warranty one. And it was a WELLS

 

Is it throwing any codes?
Mine had a similar problem and when i cleared the code 36 it cleared it all up

 

He has a code 36 also

 

I have the same probelm you have with the added pleasure of the car stalling and sometimes not restarting...you ever have that happen as well?

 

No, I haven't had the car stall on me. How was it that you got rid of the code 36? I mean aside from resetting the ECM. I did that and after 5-10 starts it comes right back. I've replaced everything in that circuit except for the ECM.

I talked with a mechanic today cuz I guess I'm just at a loss. He was telling me around $100 for a full diagnostic. I've already spent more than that trying to fix this thing so maybe it's worth it.

 

I had the codes 32-36-42. I erased the codes and fiddled with a bunch of connections and the only code that returned was the code 32. I'm still confused about that since the entir EGR system is now. I'm on my way to get the full diagnostic done as well. So, yeah, if the mechanic has the proper GM diagnostic equipment, the $100 is more than worh it. he can tell you what the code is and a ton of other things that are wrong they may not be bad enough to throw a code yet.

 

I've just returned from the shop, and the results are:

3 leaking injectors
Battery in poor condition (but I knew that already)
Faulty ECM

Apparently the computer had stored a code 42 as well as the 36, but would only flash a 36. Although I may have pulled the jumper out of the ALDL before the 42 came accross as well. Sometimes the computer will not engage the fuel pump. Also, when a fuel pressure guage was put on the fuel rail, the leaking injectors were very evident. Pressure dropped down to 0 within 3 seconds of power cut off.

So, I've orderded a set of Accel injectors, and will be getting a new ECM. I've already got a Optima battery waiting to go in. Just thought I could post this so if someone else had the same problem they might know what to expect.

 

Hmm, the ECM in my car is less than a year old, I wonder if it is an "out of the box" failure. Also, how much were the injectors?

 

A new set of Accel injectors were $238 and some change. I believe an Autozone ECM should be around $75, or it was the last time I checked.

 

I'll hold off on the ECM until I know for sure, but the injectors are a must. Thanks.

 

Ok well today I replaced my injectors with a set of Accel 24lb/hr injectors. The car starts right away and that huge puff of unburned fuel is gone from the tail. That's really great and all, but the stumble is still there. I'm going to replace the ECM tomorrow since that is the other thing the tech said was jacked up, but if it doesn't fix this problem he and I are going to have a serious problem. The only think I can think is that if the burn off function isn't occurring and there is carbon buildup or whatever on the MAF wire, the computer is getting an inaccurate reading on the incoming air. The new ECM should take care of that. But, if it doesn't...

By the way, the core charge on an Autozone ECM is damn near twice what the actual part is...something like $150.

 

yeah, it;s looking like I have a bad ECM as well. Thats a little high for a core don't you think? Lol, let us know how the ECm works cause I'm buying mine Tuesday. I'm not sure If I'm going Autozone or NAPA.

 

Guess what I found today? On my brand new Accel coil at the base of the coil wire tower, there is some very poor insulation. I could see the spark jumping around in there! It looks like that is my stumbling problem. I was spraying around water on my plug wires looking for an arc when I came accross that. So, I ordered a new one today and will send the old one back.

 

Glad you found it, it;s always nice to pinpoint the problem. I've had my IROC a year now and rarely have been able to actually find the problem.

 

I've had the same problem with an '85 Vette. I'm really curious to see what happens in your case because even after replacing the ECM, the stumble is still there.

 

Thats one thing bad about our cars. Wehn you have rough idle, there are so many things that could be the culprit and even if you do have the code, it;s still not enough. I've had extended start problems and non-start problems since I bought the car and just about everything on the car has been replaced from the ECM, fuel pump, all ignition parts, and so on. Still, no change in start up and my car will still randomly just decide not to start. Kind of discouraging, but like anything else, when she runs, she runs like a batt out of hell and I love her for it.....

 

eyerock, ive got the same damn problem!
I just got done with my 350 swap and the car will run just fine, then under hard acceleration, it will throw 33, 42 and 43 and also it would have start problems where it wouldnt even crank?? Have you had any luck yet?

 

Jimmy - I think I've pretty much narrowed down to the fuel pump relay harness and the ECM...actually, im pretty sure it was the fuel pump relay harness, but in the process of jiggling the harness to see if that was the problem, I fried the ECM. Take a really good look at that harness and then check all the connections on your ECM. Thats about all I can tell you as of now. I'm replacing the ECM this weekend so I'll let you know what happends.

 

Jimmy - I just realized what the codes you had were. You might want to have a good look at your ESC. It;s behind the Fuel Pump relay on the drivers firewall. If it;s not too expensive, you may want to consider replacing it...only reason I suggest that is simply the fact that you have two caodes for a similar function. Also, next time you get it running, tug at your MAF harness and jiggle it around to see if that changes RPM's or anything. Outta take you 5 mintues to check all that stuff, best of luck.

 

thanks man,ill check that out when it quits rainning out good luck with yours and let me know what happens

 

Mine stumbles at 3000 rpm, and sometimes dies. When it dies, the tach bottoms out on zero like i lost all ignition signal. I have a new coil, new module, new rotor, and cap.

I just bought a new pickup coil today to try as soon as my wifes car is out of the shop.

 

Yeah, if your tackh is bottoming out like that and shortly after it picks right back up, I would take a look at the pick up coil and especially the ECM to distributer ground wire.

 

When i took the distributor apart, i realized that the shield wasnt clipped down, and was rattling around some. I figure that it was interupting the signal somehow. When i was putting the new pickup coil on i realized why the other wasnt clipped. The bushing that the clips attach too is driven too far into the distributor housing, and the last clip wont attach. I am going to try attaching the shield and the coil with the same clip. I have been told that it wont hurt anything unless there is alot of pressure on the coil.

 

Lol, it;s always something. I rekon as long as you get it running, thats all that matters.

 

 

hey just a little note, i just went through this whole maf problem and drivability, code 36 etc..... i found, tps out of adjustment, set back to .540 and maf voltage fell into range, switch the burn off relay with the power relay (just to try) and code 36 gone. if you want you can visually inspect the b/off if it is working, just look at the hot wire after the car is shut off, it will glow red for a second or two, two people recommended for that task. if the wire is coming on change the relay.

 

Oil switch circuit huh? SOmeone else mentioned I should check that. Is there any elaboration you could give me on that? Also, on my car (signiture), where the heck is that circuit at?

 

stumbling problems can also be caused by egr. If its clogged from lets say.... leaky injectors.... then carbon will fill up fast on the valve and cause for a very crappy idle. Id sugest you look at that too.

 

I've considered that as well, but I replaced the entire EGR system a few months ago.

 

eyeroc as i mentioned before, check that pressure switch, then check the obvious, wire connections, grounds, voltage feeds, are you able to check if the injecters are ok are they cutting out? leaking?or to much fuel. your problem is not an easy one because so many things can affect the engine, when does it occur, while driving? at idle, what temprature range. need to know all this to narrow down the options, i've seen o2 sensors bad enough to cause this problem but not bad enough to set a code. like i said though, need more info from you brother. regards paul

 

Hey Paul
Here is all the info you need....and the O2 seonsor is new. As is the ful pump, relays, etc etc. LOL, bunch of crud huh? Any help would be awesome. From these threads, you can see it;s all the same problem, but in different disguises....I've tried everything

https://www.thirdgen.org/techbb2/sho...hreadid=193127

https://www.thirdgen.org/techbb2/sho...hreadid=190792

https://www.thirdgen.org/techbb2/sho...hreadid=180990