View Full Version : erratic idle and vacuum when a/c is on... any ideas?

08-15-2007, 07:00 PM
my vacuum is normal at idle and is fine under boost. I know all of my vacuum lines are fine. the problem happens though when I turn on the a/c. it goes from 21in hg to 18in hg, which is fine, then it starts fluttering from 15-18 as the revs start bouncing between 800 and 875. after about 10 bounces the idle finally finds itself and is fine. anyone experience anything similar? the only thing i can think of is my n75 valve since i'm running an "H" valve.

09-01-2007, 05:13 PM
my revs randomly start bouncing between 2 and 3k... then settles back down, i hvae no idea what to do...

09-02-2007, 08:57 PM
mine does this too. i always thought that its because the engine powers the ac. i think its normal.

10-13-2007, 09:23 PM
going through the same thing but much worse. anytime in drive, the revs bounce. If I put it in neutral it calms down but not where it should be. If i kick up the revs to about 1000-1100 it goes away. Vag-com pointed me to a bad sai pump. didnt want to replace it so went with the Integrated Engineering block off plate and removed that system but its still there. Now vag-com says O2 sensor intermitent so gonna try that route. holla if you find anything on your end

Fier Ringe
10-15-2007, 11:12 AM
it is common for the car to drop rpm's when the a/c compressor comes on but it should quickly return. I would recommend removing you throttle body and cleaning it with throttle body/carb cleaner and reinstalling. Then readapt your throttle. With Vag-com go into 01 engine electronics then basic settings and then channel 60 with the key on engine off. See what that does for you.