RPM surge problem when AC is on.

hi there i have the same promblem but this does when ever it feels like A/C makes no difference if on or off only had the car a week not happy but it goes back to the dealer to day (2001 s40) will let you now what they say, but i think its the electronis choke opening and closes there for let too much air in the system there for bring the revs up thats my gueses probaly wrong mind you any body else help would be much appreciated thanks

tickover compensator 

there is a electronic tickover compensator fitted, which automaticaly adjusts the tickover to the specified level to compensate for the extra load due to the air conditioning pump being used. it could also be the idle adjustment valve which is sticking and needs cleaning with carburetor cleaner, though as you say it is connected to you switching on the air conditioning, i would go for the latter. paul

took in to the dealers and they have no idea to take it back later and they said they would run it around for a couple of days to see what might be wrong:Dancing_chief: :confused_smile:

I had EXACTLY the same problem with my 2001 S60. I had the ETM (electronic throttle module) cleaned out and it solved the problem completely. Could just be muck in the induction system.