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High idle speed
I have a new problem with the idle speed. When I start the car cold, it idles around 1000 RPM. As the engine warms up, the idle speed creeps up until at warm, it idles around 1600 RPM. My thoughts were throttle body, maybe air sensor. Any other idea? I want to get in there and look at this weekend.
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10-15-2012, 09:57 AM
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Join Date: Mar 2010
Location: Texas
Posts: 2,138
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What year model is your car? It could be a vacuum leak allowing unmetered air into the throttle body.
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John Curry (Drift King) 928OC member Grand Prix White 1994 GTS AT (The GTS) Black 1989 GT (The GT) and Cobalt Blue 1989 S4 AT (The Blue Car) 1986 Euro AT Indishrot 1984 Euro S AT (The Stepson) and Black Metallic 1984 Euro S 5 speed (The Schwartz) |
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10-15-2012, 01:47 PM
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A.J.
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I have similar issue, but it does not idle as high... when started it idles at like 1000. I didnt even notice until my buddy pointed it out. Those vac lines are definitely crispy, and the plastic splitter connections are very fragile too. I should prob splurge on new silicone vac lines.
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1980 auto- cashmere beige 1984 auto- black on black |
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10-15-2012, 05:14 PM
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I have a 1982 US model. I did a cursory investigation of the vacuum lines when this first started and didn't find anything. Is there a specific one you would I suggest I focus on?
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10-16-2012, 04:12 PM
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Aux Air Valve -
Hey Bowser, If you do not seem to have a vacuum line allowing unwanted air into the intake - perhaps your Aux Air Valve has stuck open. There is a Bi-metalic strip inside the AAV that normally is open for a cold engine and closed when warm. As the engine transitions from cold to warm the AAV (which is in parallel with the throttle plate) should gradually cut itself out of the intake air circuit. If it is not working properly - the idle will gradually rise upward during the warm-up cycle.
As a test when cold and the Aux Air Valve removed you should be able to see through it's inlet/outlet ports. The colder the temp the sliding plate will allow more air to pass. It is not uncommon to initially see through only 1/2 or so of the open port with a moderate outside temp. With +12 volts/Grd applied to the electrical connector the internal heater element should gradually cause a sliding plate to block your ability to see through it. Good Luck, Michael 
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1984 928S - "Miss Purdy" 1987 911SC - "Frau Helga" 1986 930 - "Well Hung" 1975 911 Targa "Blue" Last edited by JK McDonald; 10-16-2012 at 04:43 PM.. |
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10-16-2012, 04:29 PM
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Well, I finally got to the auxillary air valve on the car. I checked the resistance and read about 50 Ohms, applied 12V to the valve and watched the plate close (most of the way in 5 minutes) and checked the voltage at the plug (12V). I did find a small (1/4" vacuum hose) inside the valve body and dumped that out. I put the car back together, drove it to warm the engine and now it idles at 1000RPM. Maybe that small hose was blocking the plate from closing. I'll have to see if this fixed it.
What is the normal idle speed? I know I can adjust that once I get it working correctly. Brian |
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10-23-2012, 05:54 PM
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Quote:
I've been trying to track down a high idle on my car too - sounds like I need to check out my Aux Air Valve too.
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1982 928 5-Speed |
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11-15-2012, 03:54 PM
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Join Date: Mar 2010
Location: Texas
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yes 690 IIRC. Check the tension of your accelerator cable, your bowden cable, and your cruise control cable.
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John Curry (Drift King) 928OC member Grand Prix White 1994 GTS AT (The GTS) Black 1989 GT (The GT) and Cobalt Blue 1989 S4 AT (The Blue Car) 1986 Euro AT Indishrot 1984 Euro S AT (The Stepson) and Black Metallic 1984 Euro S 5 speed (The Schwartz) |
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11-15-2012, 05:12 PM
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1982 Porsche 928
1980 Porsche 928
