revs itself when a/c is on...

[fr0zen]

i've had this problem since i got in an accident almost two years ago.

my car repeatedly revs itself up to 2k rpm when the a/c is on. as soon as i turn the a/c off it stops. is this common? wtf is it?

[cp[mike]]

when i turn my a/c on, the RPM's drop down... when i got the car, it made it drop down dangerously low (till i raised the idle). turning on the a/c, which turns the a/c compressor on, puts an extra stress on the running engine (why mine dropped)- the car might compensate by revving the engine higher, which makes sense, but i dont know if the car is supposed to compensate on its own or not... is urs an auto? mines a manual...

[fr0zen]

Originally posted by cpmike
when i turn my a/c on, the RPM's drop down... when i got the car, it made it drop down dangerously low (till i raised the idle). turning on the a/c, which turns the a/c compressor on, puts an extra stress on the running engine (why mine dropped)- the car might compensate by revving the engine higher, which makes sense, but i dont know if the car is supposed to compensate on its own or not... is urs an auto? mines a manual...

it doesnt just rev when the a/c comes on. it revs itself over and over and over...

common but not always easy to fix......it could be a lot of things....i'd just start with all the little things related to a tune up....if they all check out, then check for a vacuum leak......i wouldn't worry, but i know it's annoying....maybe reset the ecu and adjust the idle a bit or something

i feel like an ass when i'm at a crosswalk or something and someones walking in front of me...they think i'm revving at them... i've gotten used to just flipping the a/c off whenever i come to a stop now. i need a tune up soon anyway so maybe this crap will get fixed at the same time. would it have anything to do with having a huge stereo set up in the car? i thought maybe the additional draw of power from the a/c might be making the car rev itself to compensate?

[BustedLX]

I would check for unpluged connectors in your engine compartment. When the A/C compressor turns on the ECU changes mods to accomedate the extra load. It's possible that when you got in your accident the body shop did not reconnect everything. Maybe theres a pressure switch somewhere unpluged or something else. I don't know it's just a guess.

Also check all of your vaccum lines. They are some times the cause. Lastely the fast idle valve is infamous for going bad in the CB7 however I don't think it would be your problem since you say the problem is only present when the A/C is on.