everytime i turn my ac on the car idle goes down to about 400rpm and picks back up at around 800rpm...and while driving...i pop it out of gear and the idle goes down to 400rpm and comes back up to 800rpm...this is with the ac on. even if i rev up the engine and have it drop...it drops down to 400rpm again and raises back up...what seems to be the problem? is my idle too low?