Rockin-Iroc

I'm having a problem, and I think it's my computer dying. Usually when the temperature is cold out, while I"m driving down the road I get an almost constant interruption of power, which is momentary and lights the check engine light. Once it warms up outside, later in the day, it still does it, but not as much. When I pull up the computer codes, all I get is a repeating "12" over and over again, and according to my book, that's supposed to mean "No input to computer", or something like that.

All wiring is secure and no connections in the engine bay seem to be loose.
I don't want to go to an auto electric shop because I don't want to pay $98 bucks an hour to have them tell me, yup, it's the computer. A new computer is $114, so I thought I could try it, which would be worth about an hour of troubleshooting at the shop.

It used to be extremely intermittent but is now becoming a real pain in the butt.
Any ideas? Ever seen anything like this before?
Thanks.

High Toned SOB

I thought "12" was everything is OK. Been a while since OBD1. How about an ignition switch? I have seen those cause your symptoms. Maybe wiggle your key some while it's running, push it in and out, etc..

If you can pull your ECM out, backprobe a testlight into the Power side feeds and see if they drop out when your problem arises. That would at least tell you that it's still gettting power.

iceman02

iTrader: (1)

Rockin, sounds similar to my problem and I just found out some odd data. Don't know what it means yet, though. Do you have a laptop and ALDL cable? It would help to know what your ECM is seeing.
I didn't want to hijack your thread, so I made one of my own.... more info is available there. Do my symptoms sound the same as yours?
my thread

Rockin-Iroc

It could be the ground...I just got off reading your thread. On mine, it runs perfectly fine until "power interrupt", so I don't have quite the symptoms you do. But the reason the ground is suspect on mine is because I have had gauges stop working either permanently or intermittently because of what I think might be bad grounding. I once tried to take my dash apart and couldn't figure out how to get it all out. The whole damn thing is plastic and too much pulling and tugging will break something that I can't replace.

I think I will try to replace my ECM then. I know it's trouble shooting by throwing parts at it, but it's the likeliest cause of my problems. Illuminating the check engine light but not providing a computer code to me sounds like the computer is on its last legs and is screwing up. If it persists after changing the computer, well then that is bad. That means it's wiring, which could be a nightmare to go through. Especially looking for something so intermittent.

It's an old ECM that I bought at a junkyard, so it could be bad. Couldn't hurt to get a brand new one.

Hey, I've got another question regarding the ECM. I've got a 355 engine instead of the original 305. At the time, I just bolted on the TPI and used the stock computer, and it worked. But my injectors are 19 lb/hr 305 injectors, instead of the 22 lb/hr 350 injectors. I think I got away with it because of my high altitude and thinner air.
Well, I've got a stock 350 chip, but I never tried it because I was worried about what effect not running the correct 22 lb/hr injectors would have with the 350 prom. Would it cause any problems? Lean conditions?
Because I would like to install my 350 chip in the new ECM.

Rockin-Iroc

It turned out replacing the ECM with a spare 350 prom I had fixed the problem. We'll see how it goes. Now that it's fixed, it's snowing out, so I still have to take my truck to work.