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Registered
Join Date: Jun 2008
Location: New York, NY
Posts: 65
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80 911 SC: Sudden spike in idle RPMs? Sticky AAR? Help!
Hi guys,
I have an 80 sc targa which has been like the stock market since I bought it 6 months ago - euphoric highs, desperate lows. My latest issue is cold starting, which I'm going to have my wrench address (richen mixture, look at cold start valve). I finally got it started this afternoon and went for a drive, and 5 minutes into it the RPMs soared for no reason while I was in between gears. Idle was racing at 4k RPMs. Fortunately I was about to turn into my street so I just shut it off and coasted in my (parents') driveway. Anyone know what this could be? Do we think it's a sticky AAR? Are there any more serious problems that could be at the root of this? Be grateful for any advice. Cheers and happy thanksgiving, Adam
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"Hellblau" 1980 911SC Targa |
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11-27-2008, 02:46 PM
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PRO Motorsports
Join Date: Nov 2001
Location: Burbank, CA
Posts: 4,580
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Check that you are getting power and ground at the connector on the AAR.
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'69 911E coupe' RSR clone-in-progress (retired 911-Spec racer) '72 911T Targa MFI 2.4E spec(Formerly "Scruffy") 2004 GT3 |
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11-27-2008, 04:16 PM
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Slumlord
Join Date: May 2001
Location: Canada
Posts: 4,983
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Pinch off the AAR hose with a pair of vice grips. If idle speed slows the AAR is stuck open.
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84 Cab - sold! 89 Cab - not quite done 90C4 - winter beater |
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11-27-2008, 04:27 PM
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Registered
Join Date: Mar 2001
Location: Marysville Wa.
Posts: 22,454
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at the engine throttle housing, see that the throttle linkage is closing all the way. you usually wouldn't get 4000RPM from an air regulator issue.
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https://www.instagram.com/johnwalker8704 8009 103rd pl ne Marysville Wa 98270 206 637 4071 |
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11-27-2008, 04:33 PM
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Registered
Join Date: Jan 2005
Location: Usa
Posts: 5,573
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+1 on the throttle linkage.
Especially if the motor/transmission mounts are worn. Accelerate, shift, and the linkage hangs up, often on the engine tin where it comes up from the transmission toward the top of the engine. The linkage goes thru a hole in the engine tin. On your car, it's almost easier to stick your head under the left rear wheel and look up from the transmission pivot point of the linkage. It will pop off pretty easily. Clean the pivot points and lube them, pop the linkage back on. One way to tell if your motor mounts are bad is to jack the engine up. If you can see the engine moving up in the bay and the car isn't moving....then the motor mounts are worn out. If yours are original, could well be that time. They aren't expensive and they are easy to put in. I've gotten to put in two sets in the last year (two different cars). Jeez, maybe I should save up my money and buy a newer car (HA! NO WAY!) Hope this helps you, sticky throttles can be a most unpleasant surprise. angela
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Hello http://forums.pelicanparts.com/off-topic-discussions/1102514-we-lost-amazing-woman-yesterday.html Last edited by Laneco; 11-27-2008 at 05:01 PM.. |
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11-27-2008, 04:58 PM
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Aar..........
Even a fully open AAR (stuck) will not cause a 4000 rpm spike at idle (throttle valve partially closed). The only way this could happen is that the butterfly valve was wide open at idle and not closing properly due to some restriction. Depress the pedal accelerator and have someone look at the throttle valve stop screw.
Tony |
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11-27-2008, 05:03 PM
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+1 on the throttle linkage and maybe cruise control.
Also check your floormat that may push against the gas pedal. It happened to me. I'm messing with my AAR now and with it unplugged it will give an Idle at 2000 after warmup going through the whole phase. Nothing sudden. During warmup unplugged it goes from 1500 to 2000krpm over 5 minutes. Plugged in, it goes from 1.5K to 900rpm over about 5 min.
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78SC coupe, Silver Metallic |
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11-28-2008, 08:35 AM
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Silver 911SC
