High Idle @ 1500rpm when car warm/hot, won't kick down below 1000rpm until put in D gear

145

Asked by CML Jun 13, 2012 at 02:46 AM about the 1991 Mercedes-Benz 300-Class 4 Dr 300E Sedan

Question type: Maintenance & Repair

Been experiencing a high idle issue when my 91 300E is warm/hot. Revs up to 1500rpm and will rev down to 1000rpm when hit the gas pedal but will climb back right back up to 1500 and stay until put in D gear. Any advice?

3 Answers

485

most common is vacuum leak,could be any hose on intake,idle motor might be stuck,but I would check for leaks first,inspect,and listen for hissing noise,to only rev it up 800 rpm its probably small.

10

Not yet it don't mis there has to be a idle air valve ... I was thinking that's what airctemp sensor did. ..I tested A.I.T.Sensor shows no ohms

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