CPU replacement

[88Z-Man]

Well its time to get the car back on the road, hopefully this weekend. But the computer in the car needs to be replaced. Last summer after its complete tune-up I had the same old issue thats been doggin this car since almost day one. The check engine light comes on but there are no codes stored. It was suggested that it could be the computer itself not working properly. My question is how hard it would be to fix myself, and does the computer come pre-programed or does it need to have the info loaded at say a dealer? I have an 88 Iroc with a 350 bone stock. Some of you have seen it up at Chatterbox.

[The Fixer]

On the TPI cars, it's very easy to swap the ECM. I believe it's under the dash on the passenger side. Basically, you find it, unplug the two connectors, and get a remanufactured one (with a warranty) from the local parts store. At that point, you could either re-use your original MEMCAL chip or go with a custom chip. Replacing the chip is easy as well. On one side of the ECM, there's a small, rectangular metal plate held in place with two screws. Remove the two screws, and undo the latches to take the chip out.

[88Z-Man]

Thanks, it sounds fairly straight forward. I'll have to check it out this weekend. The dealer quoted a high price to do it so I figured I would give it a go. Can't mess it up more then it already is right? Maybe I should go with a power chip while I am at it. Gas mileage is in the basement as it is, what's a couple more MPG less.

[Tru2Chevy]

Yea, the computer is easy to change. It's just below the passenger side dash speaker.

IIRC the speaker bracket also helps hold the computer in place.

- Justin

[JSPERFORMANCE]

This would be a perfect time for a custom tune!

[Pampered-Z]

When the check engine light comes on does the car still run properly? Any hesitation? I chased the same condition, changed ( borrowed from a friend's car ) ECM and chip. Turned out the MAS was going bad and the condition kept getting worste until the MAS went bad enough to set a code.

Just be careful, you normally can't return electrical parts. You might be better off looking of a donor, or someone parting out car with same engine/trans.

What are you using to pull the codes? I use Diacom on 3rd gens, works nicely for reading the car while it's being driven and can check codes realtime.

[88Z-Man]

Originally Posted by JSPERFORMANCE

This would be a perfect time for a custom tune!

If you were not so far away I would bring the car down to ya. There are a few things I would probably want done.

[88Z-Man]

Originally Posted by Pampered-Z

When the check engine light comes on does the car still run properly? Any hesitation? I chased the same condition, changed ( borrowed from a friend's car ) ECM and chip. Turned out the MAS was going bad and the condition kept getting worste until the MAS went bad enough to set a code.

Just be careful, you normally can't return electrical parts. You might be better off looking of a donor, or someone parting out car with same engine/trans.

What are you using to pull the codes? I use Diacom on 3rd gens, works nicely for reading the car while it's being driven and can check codes realtime.

The MAS was bad and was replaced during the summer tune up because it would not pass emmisons without it. But the light still comes on. When the light is on it runs like S*** and the gas just disappears. you can almost watch the gauge drop. When the light is off it runs like a top. The codes were checked at the dealer and nothing showed up. thats what leads me to believe its the computer again. When I first got the car in 88 the computer was blowing every sensor, they finally replaced the computer and it was good for a couple years then started up again. The car was driven so infrequently since 92 or so I never bothered with it. But now that I am driving it on the weekends again I want to get this taken care of. I am afraid to drive to far because of it. Don't want to get stranded someplace.

[88Z-Man]

I took the module out this mourning and am going to get price quotes for a chip and whole new computer. Is there any way to test the computer or chip with it out of the car? Thanks Justin and TPI Monte SS, it was a breeze getting it out. I had thought that is was conected to the part under the steering wheel for them to run the codes.

[Tru2Chevy]

It is connected to that port through wiring.

Sounds like the computer is going into limp home mode. The computer just throws tons of fuel at it to keep from leaning out causing damage.

- Justin