Ok for a long time now I've had multiple problems that I think are traced to the ECM - I'm getting too much fuel and timing at certain times that isnt caused by anything else. This is probably a PROM issue, but along with that, I've got a weird problem where my car will all of a sudden go into what I assumed was "Limp Home Mode", but now I'm not sure - it may be "Fail Safe Mode", but I really dont know the difference - it loses most of its power and bucks and struggles like crazy, and the SES light comes on. I have tried unsuccessfully to retrieve the code by the normal method - all it ever gives me is the standard "12", like the code never happened and is automatically cleared. This shouldnt happen, am I right? Does this reveal a failing ECM processor or something like that? I really dont know what to do.....what do you guys think it is? IF it is the ECM, what does it cost to replace it and where do I lookl? Thanks.

 

Thought I might mention - as far as the too-much-fuel thing, the exhaust smells a little rich and I think I have fuel combusting in the exhaust at a set RPM that sounds like a rattle. As for the timing, its revealed by engine knock and happens randomly now and then when I'm at WOT. However, neither of these things has to necessarily happen for the car to go crazy and go into the limp home mode I was talking about. Sometimes the events coincide, but half the time everything is fine and the problem comes out of nowhere. Hope that helps. Thanks.

 

Interesting problem. Drop the ECM down and start it. With a screwdriver handle tap on the ECM while it's running. See if the problem can be generated that way. I have seen a few do that on other GM models, they run rough and a whap from the driver cures it. No codes indicates most major components are OK. Before replacing ECM try wiggling wires under the hood with it running to duplicate problem. Rule out everything else, over half of the ECM's sent to GM repair depot's check fine.

 

You might want to see if the ignition coil or ignition module are to blame. Buy a cheap new ignition coil from somewhere and see if it solves it, if not then return the coil. Do the same with the ignition controll module. If you are lucky you might be able to get good working parts from a junkyard.

 

I just went through a simmilar situation, after replacing everything that you could ever relate to the condition, pickup coil, control module, ignition coil, EGR, ECM, fuel pressure reg, fuel pump relay,o2 sensor, TPS, IAC and a few others.Guess what was the actual culprit? 1 stinking periodically malfunctioning injector. I learned from a knowlegeable mechanic that the injectors are pulsed from ground and that if you have 1 that goes to a malfunctioning state (not clogged) it will rob ground from others in that bank, maybe other bank as well. Thus you have a car that runs like crap. My situation was that sometimes it would run fine and other times it would sit there and run like what you describe. It eventually stayed in the later condition. If your car is in the current state of herky jerking around, try to get under dash and pull either inj1 or inj2 fuse individually and see if engine smooths somewhat. Better way is to isolate one injector by unplugging each injector @ a time to see if you can isolate bad one. Give this some thought and give it a try, I would have saved a lot of time and money had I known this before I did.

 

Ok great suggestion! If this is the problem, do I just need to have them cleaned or replaced?