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Registered
Join Date: Feb 2009
Location: Tenino, Washington
Posts: 41
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warm engine idle surging
My 1986 911 has a weird problem. The cold start-up idle is a little screwed up. It's way too rich, and it doesn't stay on long enough. I live in a temperate climate so I'm not too worried about it unless it's related to the problem below. I figure the cold start idle issue is most likely a cylinder head temp sensor or the idle air control valve...I'll get to them later when I feel like busting a knuckle.
The one that's got me beat is a temporary problem I only get when the engine is at normal operating temperature, and more often on warm days. The car usually idles at around 1000 or a little less, by every once in a while, when you take your foot of the gas and coast to a stop, the engine will begin surging between 0 and normal, very rhythmically and fairly fast. The car never dies and you can usually make it stop by turning the car off and starting it again...this happens maybe once a day at most. Any ideas? Gordon |
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07-05-2009, 05:54 PM
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muck-raker
Join Date: Jan 2009
Location: Coastal PNW
Posts: 3,059
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Either a rich mixture causing the surge, or the throttle linkage on your tranny housing is sticking (a common warm-weather problem). Check, clean and lube that linkage first before moving to the next possible solution.
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STONE '88 Cabriolet, using EP Slick 20w50 partial synthetic Snake Oil...just as Rommel intended.  Deny Everything; Admit Nothing; and Always Make Counter-accusations 
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07-05-2009, 06:25 PM
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Make sure the idle microswitch on the throttle body is engaging properly. As kidrock said, a misadjusted throttle linkage can cause the throttle to not completely close.
With the engine not running push the throttle open in the engine bay and let it return to idle. You should be able to hear the faint click of the microswitch. If you have to pull the throttle against the close position by hand to make it click there is your problem. ingo
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1974 Targa 3.6, 2001 C4 (sold), 2019 GT3RS, 2000 ML430 I repair/rebuild Bosch CDI Boxes and Porsche Motronic DMEs Porsche "Hammer" or Porsche PST2, PIWIS III - I can help!! How about a NoBadDays DualChip for 964 or '95 993 |
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07-06-2009, 12:00 PM
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Join Date: Dec 1999
Location: Novato, CA
Posts: 4,740
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Quote:
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07-06-2009, 05:58 PM
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1974 Porsche 911 Targa 3.6
