Engine hunting at idle

[McClintock]

I have an 89 corsica with a 2.8 engine. Yesterday my wife tried to start it and the battery literally exploded. It got acid in the area of the battery, but nothing too severe. I put baking soda on the acid and rinsed it off with water. I put a new battery in and checked voltage with it running. It was normal at about 14.4 volts, so I can only assume that it was a bad battery.
Now, since I replaced the battery, at idle it hunts...goes up to about 1300rpm and down to about 400. If I'm lucky it doesn't die, but it usually does. I have tried cleaning the IAC valve, which did not help at all. Also, I tried disconnecting the battery and resetting the computer. After I reset it, I started the engine and let it idle about 5 min. It did good for the first couple of minutes, then it started hunting again. After a couple of cycles of hunting, it would die. When it died, it would not restart without me giving it a little gas. I have checked for codes and none show.
Any help would be greatly appreciated.

[bowtiebandit]

Well normally you would need a scan tool to do what is called an idle learn procedure but try this. Start the car, with parking brake applied put it in gear foot on brake and wait for the coolant fan to come on. Then take it on a long highway trip, 20 miles or so and that should do it. If not you'll have to try a dealer I'm afraid.
Basically what has happened is the ECM has lost its memory of how the cars settings where and is trying to relearn, TPS, IAC, throttle angle, idle speed and so on.

[Shortbus]

Yeah what bowtie said

[McClintock]

Thank you! I think it worked. It has helped out a lot. I took it out today and it never died. Sounded like it might die a couple of times, but nothing like it was doing.

[pcv]

I'd clean the throtle body on this one. Works wonders after a battery has been disconnected.

[Flatrater]

On the older 2.8l engine in the mid 80's to the mid 90's the IAC was told where to go by the ECM, when you disconnect the battery the memory was gone and the ECM would have to relearn the IAC to work right and the procedure Bowtie stated is the correct way.

[CRX89]

I have the same problem to. I have a 93 with 3.1 and I disconnected the battery and it does the same. So let me get this right. I start the car with the parking brake on. 2 put it in reverse or drive(any gear) and when I hear the cooling fan come on I release the parking brake and drive 20 or so miles on the freeway and it should go away? If it doesnt should I buy a scan tool or new IAC and try the same thing again? Thanks guys. Im a NOOB to the 3.1. Hi everyone

[Judas]

I know this is an old thread but for people like me who stumble upon this page while searching for the same solution.

I solved my problem by resetting the IAC. To do so: turn the ignition on (without starting the car), turn it off or ten seconds, then turn it back on and start the car.

Before you start replacing parts, give this a try.

[Kooterskkar]

Al you need to do is relearn the ECM. Very simple. Reconnect the battery, start the car and let it idle until the idle smooths out. Usually about 3 - 4 minutes. Once it smooths out cut it off. Restart it, and take it for a short drive (10 - 15 minutes) on the interstate.