Idle jumping up and down

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Posts: 8
Joined: Wed Apr 04, 2018 2:12 pm

Idle jumping up and down

Post by Bareld »


My E12 1981 has a m30B28 engine. I have an issue which seems hard to solve. Car runs great but when I stop and car goes to idle the rev is going up and down. Sometimes even stalls. After 3 ,4 times the idle goes steady to 950 rpm
I’ve checked all I can think of. Valve clearance, throttle body adjustment, ignition timing, new plugs and ignition wire TTS and cold start valve works as it should
Anybody has an idea what to look for?
canada karl
Posts: 965
Joined: Tue Jan 06, 2009 3:50 pm

Re: Idle jumping up and down

Post by canada karl »

Maybe check all the vacuum hoses. i think these motors are sensitive to vacuum leaks. Could be a tear in the rubber or a leak that is not visible. Even if the dip stick is not pushed all the way in it can create a vacuum leak.
1976 530i. BMW 59 Triumph TR3A(rolling resto). 67 Triumph TR4A(salvageable). 86 900S Winter car
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