I would still check the voltage to the Throttle Position Sensor, or just replace it and if that does not cure your needs, take it back. Man, that's a tough one. Well if the engine is surging up upon a stop, something is keeping fuel running to the engine for whatever reason, thus you are getting the surge. For whatever reason, the overall system isn't keeping up with what's happening in "real-time". Computer perhaps? But, if the TPS wasn't functioning correctly, the EEC would be getting inaccurate information about how much fuel to send and surging/stalling would occur. Tough one.

 

With the AC completely off and the car in gear idle is about 750 RPM's when i put it in park the RPM drops to about 450 and then surges to about 1100 and then like it is overreacting it drops down to about 450 again and does this about 4 times Thanks for the help.

 

If it also does it with the A/C off it could be either the TPS sensor or a bad idle motor.

 

I agree.

 

Tech, i have a 93' 940 turbo, and i am having the identical problems. when i idle or come to a stop at a light and the ac is on, the rpms fluctuate severly at times and the compressor seems to make a low pitched rumbling noise. this problem does not however occur when the ac is in off position. when i start up the car, the service engine light comes on, but only for approximatly 2 min, then turns off. this problem has been going on for maybe 2 months....any help would be much appreciated.

 

Your A/C compressor might be on its way out.The rubbing usually means the clutch slipping.

The SERVICE light is a reminder light for oil changes.

On the 940 remove the rubber plug in the speedo assembly and push the little black button to reset the light with the key on.

 

thanks alot tech....just curious, do you have any idea what a replacement compresser would run? i would guess a few hundred, but you'd prolly have a better idea. thanks again!

 

I think it is between $300.00 to 500.00 depending on where you go.

For a little better of an idea if the compressor is going. Look at the clutch on the compressor and see if it looks rusty or black like it is burnt.