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Kurt
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1983 911SC CIS - fast rpm drop and occasional RPM hang up
Mostly stock 1983 911SC, when depressing the clutch and there's no load on the engine the RPM drops really fast, so much so that when coming to a stop at a stop light the engine will often stall out.
Additionally, every so often the RPM will get hung up and stay elevated for an extended time. I was thinking maybe a bad decel valve/vacuum limiter. Otherwise, everything is running like a top. Thanks for the input! Sent from my Pixel 9 Pro XL using Tapatalk
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Kurt - 1983 911SC |
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04-21-2025, 07:20 AM
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PCA Member since 1988
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I'm thinking bad decel valve too. Disconnect and bypass it to see if that makes a difference. I'm not sure whether your 1983 has the adjustable type decel valve (those have a setscrew and locknut on the top). If so, try adjusting it.
On my 1980 RoW engine, I just removed it.
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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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04-22-2025, 12:22 AM
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Registered
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Also make sure your throttle linkages are not getting caught on anything (with your hung up rpm).
Several places - at the pedal, under the car by the clutch cable, and at the throttle housing itself - check you have all the springs in place. Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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04-22-2025, 08:00 PM
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PCA Member since 1988
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^^ Alan is right--check the simple stuff first.
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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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04-23-2025, 10:37 AM
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1983 Porsche 911SC
