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Cause of rising idle speed and richer mixture??
In the neverending battle to get my '80 SC to start and idle as it should, I hooked up the Gastester today and fiddle with the mixture for a while. When it was warmed up, I had a mixture of 3.3, not too bad I thought. Tweeked it to 3.5, where it stayed for several minutes. As the engine began to get hotter, the mixture went up and up and up as did the idle speed. I would keep tweaking it back to 3.5, but it would keep climbing over the course of several minutes.
I know that several people have commented how CIS cars' idle speed can creep up with engine temperature, but what's the cause of this. I assume the increase in fuel is causing the increased idle speed, but where is this excess fuel coming from? Something that can be fixed or something that I'll have to live with. I don't recall it being this bad when I first got my car however.
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'80 Targa - Gone. No P-car until I have more time and money My Pelican Owners Page |
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08-19-2004, 01:41 PM
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Designer King
Join Date: Mar 2004
Location: Toronto, ON Canada
Posts: 5,499
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I wonder if you have a vacuum leak, or maybe your WUR is off and is not raising the control pressure as it should as the engine gets hotter.
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Paul Yellow 77 Sunroof Coupe/cork interior; 3.2L SS '80 engine/10.3:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rods; Bilstein B6; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Firestone Firehawk Indy 500s; PCA/UCR, MID9 Never leave well enough alone |
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08-19-2004, 02:46 PM
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Registered
Join Date: Oct 2001
Location: San Carlos, CA US
Posts: 5,520
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Where are you sticking your meter probe?
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Porsche 2005 GT3, 2006 997S with bore-scoring Exotic: Ferrari F360F1 TDF, Ferrari 328 GTS Disposable Car: BMW 530xiT, 2008 Mini Cooper S Two-wheel art: Ducati 907IE, Ducati 851 |
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08-19-2004, 03:25 PM
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I'm putting my probe into the exhaust tip as the Gunson directions dictate. My cat is hollowed out so that doesn't interfere with the readings. I think I'm definitely chasing a vacuum leak, because I don't get any noticeable idle speed drop when I remove the oil tank cap. That would make me think that I have the mixture rich enough to compensate for the vacuum leak.
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'80 Targa - Gone. No P-car until I have more time and money My Pelican Owners Page |
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08-19-2004, 07:01 PM
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1980 Porsche 911SC Targa 3.0
