380SL has Unstable Revs

My 1981 380SL developed a problem recently, where when idling and in park, the idle revs jump from 700 to about 1200 for a few moments and then back down. What should I look for in fixing this? Is it dangerous?

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- Michael J. Astrauskas


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The idle speed motor on top of the front of the engine is controlled by a computer mounted in the right kick panel. Take this box out open it and resolder the connections to the pinout. Less likely- poor connection at the idle motor.
Bill Ditmire Ditmire Motorworks,Inc. 425 White Horse Pike Absecon,NJ 08201 http://www.ditmire.com 609-641-3392
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I've had similar problems on other vehicles which may or may not apply to your 380SL. On most cars that have power steering, if the pressure in the system gets too low, the idle speed will be increased. Idle speed is also increased when the A/C compressor is running. A fault here could be causing the problem.
When I had this problem with my Jeep Cherokee, yes, it was dangerous! Often, while parking, the engine RPM's would suddenly jump causing the car to lurch. Scared the s**t out of my wife a couple of times.
Steve

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Doesn't apply, we're talking Mercedes here no guess work on this problem, Bill Ditmire got it right the first time, Idle speed control unit, 380SL = R107, idle speed control unit located behind the glove box. Cheers. Martin. Autobahn Auto
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