idle surge when brakes applied

C

Campbell

New member
Hi, is it normal for the engine to surge a couple hundred rpm when the brakes applied and released at idle? Its a A2 (1987) scirocco. I'm wondering if the vacuum booster is bad - have changed vacuum lines. Thx
 
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If it's a short-term surge, that sounds iffy but not too bad. If the idle moves and stays while you're on the brakes, then I'd suspect a bad booster.

another way to check is to stick a vacuum pump & gauge on the booster. Try to pull a vacuum on it and see if it bleeds down with time.
 
Yes, it will move a little RPM.
Check the O ring on tha back of the MC. It needs one to seal, not many MC come with, and it is easy to leave out.
MM
 
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