92 chevy lumina 3.1 changed computer


Old 10-12-07, 08:03 AM
Thread Starter
Join Date: Oct 2007
Posts: 1
92 chevy lumina 3.1 changed computer

Hi.. I am new and hope you can help me.
I have been having trouble with my lumina with a heavy smell of gas and using it very fast. I was told by the Chevy dealer the computer needs changed. Ok I did it myself. I got a computer off a 92 lumina 3.1 and the numbers matched. The PROM number did not. So I put my PROM in from the old computer.

The computer fixed the gas smell and the fuel mileage is a lot better. It does not sound any better (has a miss sound). Any way and new problem has arrisen. It shuts off when you slow down to stop or really slow to make a turn. Other wise is runs like a raped ape.

My question is should I have used the PROM from the old computer or should I have used the one that came with the computer since it came off the same year and model as my car? Or should I be looking else where?
Oh when it does idle or just before it dies at a stop sign it lurches (sound wise) you know kind of like it starving for air or gas, then getting it.
Thanks cj
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Old 10-12-07, 06:13 PM
Join Date: Feb 2005
Posts: 579
The idle relearn needs to be done. We always do this with a scan tool. I have heard that if you drive the car around 40mph for an extended time, the IAC will relearn itself. Don't know, never tried it.
Old 10-12-07, 06:23 PM
Join Date: Sep 2007
Location: wisconsin
Posts: 73
i remember there was someway to learn it by running it 10 minute turning it off running it again
I would say easy way would be to just find someone with a scanner to relearn it for u
Old 10-12-07, 08:22 PM
Join Date: Dec 2001
Posts: 2,538
would start by cleaning around the throttle plate with carb cleaner, common problem when computer or battery is disconnected, if the throttle plate is gummed up it restricts airflow used for base idle speed and the computer has problems relearning the idle speed otherwise the ecm should have no trouble relearning the idle and does not require a scanner.
Old 10-13-07, 08:56 AM
Join Date: Sep 2007
Location: wisconsin
Posts: 73
the early 90s and late 80s 3.1 did need the idle reset when a battery disconnect happens there is a specific procedure in the service manual for it

they will not relearn it on there own

below is a copy from one manual

Any time the battery is disconnected, the programmed position of the Idle Air Control (IAC) valve pintle is lost, and replaced with a default value. To return the IAC valve pintle to the correct position, perform the following procedure:

After restoring battery power, connect the Tech 1 or equivalent "Scan" tool.
Select "IAC System," then select "Idle Learn" in the "MISC TEST" mode.
Proceed with idle learn as directed.
Old 10-13-07, 03:27 PM
Join Date: Dec 2001
Posts: 2,538
the iac counts do go to a default value wich usually isnt high enough on vehicle with alot of carbon build up around the throttleplate wich results in the vehicle dying and ive never needed a tech 1 or scanner to get the computer to relearn the idle, overtime iac counts continue to go up to compensate for buildup around the throttle plate this is the computers memory that is lost when disonnect of the battery.
you can take about any gm car with alot of buildup around the throttle plate hook up a scanner and monitor iac counts at a certain rpm and do nothing but clean the throttle plate and observe how much iac count lowered just from getting its base airflow back around the throttle plate.
Old 10-13-07, 03:35 PM
Join Date: Aug 2007
Posts: 6
After reading this, I hope I dont have to do the same thing, because I have a idle problem....


Old 10-13-07, 04:02 PM
Join Date: Sep 2007
Location: wisconsin
Posts: 73
yes u can clean the throttle body and drop the iac counts i will not argue that

i will not argue that point i am just giving the correct info regarding the idle procedure for this type of car ask any gm tech who has been around a while he will tell u how many cars back in the day we have seen come in with idle low or hunting do to customer disconnecting the battery
Old 10-13-07, 05:49 PM
Join Date: Dec 2001
Posts: 2,538
im well aware of the problem having seeing many of them coming in to the shop, often just from a normal battery change however that doesnt mean that it affected all early model gms many didnt have an idling problem after replacing the battery only those with excessive buildup around the throttle plates had the idling problem once cleaned you can disconnect the battery as many times as you would like and never have a problem with the ecm relearning idle strategy.

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