|
|
|
|
| Author |
|
|
Registered
Join Date: Dec 2009
Posts: 16
|
wondering idle on a 1982 911SC
Does anyone have a permenent solution to a wondering idle (from about 800-1400rpm) on the 3.0 with the CIS injection system?
|
||
12-09-2009, 07:52 AM
|
|
|
Dixie Region R Gruppe
|
Could be a number of things. It seems like the winter time allows it to show its face. Did you check for vacuum leaks? Does it only do it while it is cold?
I would do a search for CIS trouble shooting on here and you will probably see a few ideas. Phillip
__________________
Instagram @phillipkj4 1980 911 SC Backdated Viper Green 1992 Ferrari 348TB |
||
|
12-09-2009, 07:56 AM
|
|
|
Somatic Negative Optimist
|
It's a wonder that some engines even run.
 Wonder what it could be?  Doesn't sound like hunting with that much difference in RPM. It's an '83 but more maintenance history is needed to give an opinion. Tune-up? Distributor ever cleaned/oiled/serviced? Throttle linkage jammed by the clutch cable near the bell crank? When does the RPM change? During cold-start? At a red light? When doing what?
__________________
1980 Carrerarized SC with SS 3.2, LSD & Extras. SOLD! 1995 seafoam-green 993 C2, LSD, Sport seats.  Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ". 
|
||
|
12-09-2009, 09:45 AM
|
|
|
Registered
Join Date: Oct 2006
Location: MYR S.C.
Posts: 17,321
|
that would make for a serious rich condition. surprised it does not cut off if you give it gas and let the RPM's drop.
check fuse 18 for the dme relay power to the WUR, 12v. control pressure. that order because of ease.
__________________
86 930 94kmiles [_ _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
||
|
12-09-2009, 10:09 AM
|
|
|
Registered
Join Date: Feb 2009
Location: Knoxville, TN
Posts: 1,347
|
I unplugged my o2 sensor on mine, and its rock solid 800rpms.
|
||
|
12-09-2009, 10:30 AM
|
|
|
Somatic Negative Optimist
|
It's an SC and SC's have no DME.
 Carreras have DME. '83 SC's have a Lambda ECU under the pass seat and when it doesn't work, the engine runs very rough in idle but no resulting increase in RPM and no surging or hunting.
__________________
1980 Carrerarized SC with SS 3.2, LSD & Extras. SOLD! 1995 seafoam-green 993 C2, LSD, Sport seats. Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ".
|
||
|
12-09-2009, 11:09 AM
|
|
|
|
Registered
Join Date: Oct 1999
Posts: 8,673
|
I wonder why it wanders?
SC should idle at steady 950 RPM, unless it's just been started cold. |
||
|
12-09-2009, 12:44 PM
|
|
|
Registered
|
check your air/fuel mixture.
__________________
poof! gone |
||
|
12-09-2009, 12:45 PM
|
|
|
grateful user
|
when your 02 sensor craps out, the ecm goes to a fixed duty rate, and could result in to rich a mix on a warm engine
__________________
fully disassembled, blasted, customized and restored 75 targa with factory hard top, 993 style turbo ft fenders, steel flares, C2 bumpers and rockers, 82 3.0 sc 9.5/1 engine with PMS flywheel, 964 cams, flowed heads, ssi's short geared 915 w/lsd, polybronze, bilstein,working lambda, modified and highly tuned cis, tensioners, pop valve, backdated exhaust and heater, 2300 lbs. no bolt left untouched. 1970 911E. Nice car but needs a re-do. |
||
|
12-09-2009, 02:15 PM
|
|
|
Recreational Mechanic
|
Disconnect your O2 sensor. Reset mixture to 3-3.5% CO measured at the tailpipe. Problem solved. Idle hunts b/c frequency valve is trying to play with fuel mixture to meet emissions demands of the O2 sensor. Disconnecting pegs the Frequency valve at fixed position, 55-60% open I think. Vacuum leaks, even small ones, can contribute to the frequency valve idle hunting.
__________________
P Cars: 2022 Macan GTS / One empty garage space ---- Other cars: 2019 Golf R 6MT / 2021 F-250 Diesel / 2024 Toyota GR86 6MT ---- Gone: 1997 Spec Boxster Race Car, 2020 GT4, 2004 GT3, 2003 Carrera, 1982 911SC, 2005 Lotus Elise and lots of other non-Porsches PCA National DE Instructor #202106053 / PCA Club Racing / WRL Endurance Racing |
||
|
12-09-2009, 05:29 PM
|
|
|
Drive it like u stole it.
|
I had a very similar issue on a 76 turbo motor years ago. It turned out to be the WUR. I used a gauge set to test system pressures at various points in the CIS system and narrowed it down. Order one from our host if you don't have one. They are invaluable in trouble shooting CIS.
__________________
____________________________ Bill Jones Jupiter, FL 77 Euro 911 3.0 Wide Body - under construction http://www.flickr.com/photos/rennsport/collections/72157618856489537/ |
||
|
12-09-2009, 05:43 PM
|
|
1979 Porsche 911 3.0
Backdated 911
1968 Porsche 912
1974 Porsche 914
ME 262 (SOLD)
Colibri
Gas Mizer
Mileage King
Dog Bus
75 Porsche 911
bike
1970 porsche E
911SC 3.0
Project Car
