idle too slow to drop

[aussiejohn]

Hi Guys

1989 BMW 525 i manual.....car idles fine when the air conditiner is OFF....however when the air is ON.... the car idles fine but is very slow for the idle to return to normal when the revs are increased and I take my foot off the accelerator.....eg when driving and changing gear (say from 1st to 2nd ) I have to pause in neutral for several seconds for the revs to drop......with the air OFF it is OK.....I have replace the idle control valve but has made no difference.....any ideas ?????
Cheers
Aussie John

[Tiger]

Vacuum leak is probably the most likely cause. Spray carb cleaners tof ind the leak.