Had to replace my battery this week. Now whenthe car is idling, it will fluctuate between 500 and 1000 rpm. Sometimes it nearly stalls when shifting from reverse to 1st just when backing out of the driveway. Did not happen prior to battery change.
97 850 wagon non-turbo, 5-speed

Thanks,
Tom

 

Please check if the contact on the negative pole on the battery is tight.

You also might have to retrain the ECU after swapping the battery, I'm not sure.

 

It might need to relearn some have to others don't.

 

If the ECU did need to re-learn a little bit of the fuel maps and all it shouldn't happen everytime you start the car.

Check your battery connections.
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Good evening,

If the battery connections are good, and the new battery isn't low on electrolyte (I've seen some franchise batteries that were low on electrolyte, even though they were new. I now only use Interstate Battery), try making the ECU re-learn idle:

---ADDED ON FEB 9 FRIDAY---
*Before beginning the below procedure, disconnect the negative battery cable and leave it for approx. 20 minutes for the ECU relay to completely turn off (reset). Then, re-connect the negative cable and start the following procedure:

1. Turn off ALL electrical loads (I even disengage parking brake, so that the parking brake light on the dash doesn't light).
2. Start the engine, without pressing on the brake pedal (be sure that there is nothing in front of you).
3. Let the engine idle for 10 minutes. Do not turn on any electrical load, not evenparking lights. Try reading a bookor something, don't turn the radio on , either.

If this does not solve the problem, the battery seems skeptical. Modern cars are extremely sensitive to correct power supply, even a slipping accessory belt/loose fuel capcauses engine performance problems.

I hope this helps,


JPN