My '89 RS with the 305 TBI has been idling strangely. I posted topics in the TBI section and I still haven't found the problem. I have pretty much eliminated any possible vacuum or EGR problems.

The car idles erratically (600 to 800 then back to 600 and so on in drive) after it's warm and especially after you've been romping on it. It also pings when the RPMs drop with every upshift. The erratic idle but not the pinging has been reduces a little since I started using a different gas (went from 88 octane to 89) The timing is correct, the gas mileage is good and the check engine light is staying off ( although I did get a code 32 a while back that hasn't come back since i cleared it up)

There hasn't been a loss in performance, and the car runs perfect when it's cold.

The reason I think it might be the ECM is because the erratic idle seemed to be consistant with a change in the clicking of the injectors that I noticed when I ran it without the top on the air cleaner for a few minutes.

Any ideas???
thanx

 

I would check the coil, and/or the pickup coil (does an 89 even have a pickup coil?). Also test out the temp sensor. It may be erratic and sending bad data to the ecm. Also, surging is sometimes caused by a bad fuel pressure regulator or pump. The only way I know to test the ECM is by verifying the sensors first then reading the ALDL data and see what the ECM is seeing. If the sensor data is way off from the ECM data, most likely it is the ECM. But take caution, grounding ALWAYS plays a factor. Make sure all the grounding is OK.

Oh, and a couple cans of Seamfoam can work wonders!! Use it from your brake booster vacuum line and add a can or two to your fuel.

Just a couple of suggestions before spending the kind of money needed for a new ECM.

 

Might try unpluging the IAC connector on the highside of the swing. That will freeze the IAC and determine if the ECM is commanding the idle to move. Might also verify your egr valve isn't sticking when warm.