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Join Date: Sep 2017
Posts: 66
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'86 problems idling hot and cold
Howdy all!
driving the 86 stock 911 today and on I95 in traffic, the poor thing kept cutting off. It has the fabspeed exhaust, steve wong chip and a completely re-gasketed / hosed intake system, including the manifold spacer blocks. However, it does not like to idle when cold (ambient temp below 70) which is annoying but once the car warms up it will be fine or apparently when hot either. Tips? suggestions? Thanks! Andrew |
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06-19-2023, 10:59 AM
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PCA Member since 1988
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Could be a lot of things, but I'm thinking temperature sensor likely.
How does it "cut off"? Poor running then dies, or like a light switch?
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1973.5 911T with RoW 1980 SC CIS stroked to 3.2, 10:1 Mahle Sport p/c's, TBC exhaust ports, M1 cams, SSI's. RSR bushings & adj spring plates, Koni Sports, 21/26mm T-bars, stock swaybars, 16x7 Fuchs w Michelin Pilot Sport A/S 3+, 205/55-16 at all 4 corners. Cars are for driving. If you want art, get something you can hang on the wall! |
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06-19-2023, 12:01 PM
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I will double check the temperature sensor.
It dies like the ECU forgets to catch the motor. Just revs down to off. So like a switch? Rev to ~2k in first hold that speed as we creep forward 30 yards, clutch in as traffic stops, engine rpm drops as soon as clutch goes in but never hits idle, just dies. Did that make sense? |
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06-19-2023, 12:26 PM
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PCA Member since 1988
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If it's "on-off" type of behavior, that would not indicate the temp sensor. A bad temp sensor usually causes rough running, stumbling, hard starting, and the like. You described hard starting, and that's why I thought temp sensor.
More likely you have an intermittent connection somewhere, or a bad crank sensor, or something inside the ECU or DME relay. There are others here who have better understanding of those problems than I do, and you will notice that there are several parallel threads about Carerras with those problems. But let me ask some more diagnostic questions. When it dies like that in traffic, does it restart quickly, or does it struggle to restart? (I assume the engine is fully warm at that point). Does it run normally except when you push the clutch in and take your foot off the gas? Did this problem just start or did it start after you had done something else to the engine (you described replacing the gaskets and hoses)?
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1973.5 911T with RoW 1980 SC CIS stroked to 3.2, 10:1 Mahle Sport p/c's, TBC exhaust ports, M1 cams, SSI's. RSR bushings & adj spring plates, Koni Sports, 21/26mm T-bars, stock swaybars, 16x7 Fuchs w Michelin Pilot Sport A/S 3+, 205/55-16 at all 4 corners. Cars are for driving. If you want art, get something you can hang on the wall! Last edited by PeteKz; 06-19-2023 at 12:44 PM.. |
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06-19-2023, 12:41 PM
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I sure wish I was better at searching to find other like threads.
Yes, the car re-starts easily enough. |
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06-19-2023, 03:06 PM
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Location: Lomita, CA
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Quote:
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Dave |
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06-19-2023, 03:18 PM
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New-ish 911SC Targa Owner
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It sounds like it maintains running if you keep the throttle cracked enough. Otherwise, if you rely on the idle control valve to supply the air for combustion it fails and stales out.
I think there are some tests for the IACV that could confirm if its defective or not. I would start there.
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'83 Targa 300k w/ freshened 3.0 with 930/52 case# 6770540 ARP and Raceware hardware - AEM Infinity 506, Triumph T595 ITBs, B&B headers, Dynomax muff, Fidanza FW, Alum PP-203whp |
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06-20-2023, 05:03 AM
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For the longest time I too was convinced that the IAC was bad, not listening, etc. I went so far as to create a IACC (Idle Air Controller Controller) which proved that the IAC was good. But when I rebuilt the intake, I replaced the IAC anyway (because, while you are in there...)
My hope with the IACC project was to be able to manually adjust the idle (or at least IAC position) Should I re-open this project? Supposed to rain the next week here on the east coast, I will test the temp sensor and adjust vector there, too. |
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06-20-2023, 06:08 AM
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Jeanine
