hello everyone!

newbie here so take it easy..

just bought a 99 S80 2.9 with 140k miles, had i read here first, i probably would have never bought it..


so, everytime i run the ac and the car sits in idle, i watch the rpms jump between 300-900, as if it will shutoff but never does.
i dont feel a difference while driving or while stopped, only when in neutral or park.

does that make any sense? any ideas please?? thanks!

 

welcome to 'the club"! Not sure but i don't think it got anything to do with AC. I had the same problem but it went away after etm recall was done. Just call your local dialer for appointment (and in my case they didn't even charge me for diagnostic) . good luck.

 

so no one experience RPMs jumping around when AC is on?

 

bahroor: I am experiencing the same engine rpm surge as you and also believe it is related to the when the AC is on.
I had owned my 2001 S80 2.9 for 3 months (purchased in March 2007) when it started the RPM surge. This caught me by surprise when the car leaped forward at a stop light. I took it to the local dealer after and found that there was a throttle recall a few years ago that was supposed to fix this issue. This is a software update and was done for zero cost. Not so good was two weeks after this was done, the issue returned. As yet there is no answer by the dealer.
This happens usually when the car is warm and the AC is on. sitting still, with the trans in park, the RPMs jump from 400 to 900 and this continues until the car turns itself off. If I turn the AC off while this is happening, the RPMs return to a steady idle of 550 or so. Turning the AC back on (hitting the AUTO button) and after a minute or so, the RPMs may or may not start the surging again. I have noticed this happens more often if I have to stop quickly. I have heard suggestions of vacuum tubes being bad to AC going bad. But as I said, nothing found for sure as yet.
goteborgS80..

 

Try cleaning the throttle body if it continues to do it then the throttle body is bad.
That is if the recall software has already been installed.

 

I would put the MAF (mass air flow) in your list of things to checkout if it's not the ETM.