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It'say too lean if it stumbles and dies. When it's way too rich the idle will surge and hunt up and down. The 911SC has a deceleration valve to help keep the RPMs up after you lift off the gas pedal. It is designed to keep you in the right RPM range while shifting. Look into to this feature on your car and see if you can richen up your mixture. If you hook up your O2 sensor while warm and your idle picks up then it needs more fuel.
mike |
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10-07-2004, 06:35 AM
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Somewhere in the Midwest
Join Date: Oct 2001
Location: In the barn!
Posts: 12,499
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Alex, you have a DME engine ('86 Carrera)...there has been a lot of discussion on the driveability of the 3.2 engine. Disconnecting the O2 sensor on the DME is not going to fix much... my guess...search "speed sensor" (flywheel speed).
Don't confuse the disconnection of the O2 sensor on a CIS engine with disconnection of the O2 sensor on a DME engine. |
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10-07-2004, 07:04 AM
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Registered
Join Date: Feb 2002
Location: Asheville, NC
Posts: 1,415
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Quote:
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Gone but not forgotten - 1980 Porsche 911SC w/ -22mm/28mm Torsion Bars | Custom Valved Bilsteins | 22mm/21mm Carrera Sway Bars | Elephant Poly/Bronze Bushings | Carrera Brakes | AJ-USA Brake Cooling | Carrera Oil Cooler w/ Fan | Elephant Strut Brace | Oh, and no ABS or PSM or A/C |
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10-07-2004, 06:16 PM
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Registered
Join Date: Aug 2004
Location: Northern Virginia
Posts: 437
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Started my car this morning after I thought I fixed the air leaks and it bounced from 500 to 1500 back and forth for about a minute.
At lunch I decided to mess with the CO mixture ath the AFM and got the car to perform much better. I don't have a CO analyzer, I just winged it at experience the surging when it was too rich and the slight puffing when it was too lean and stopped in the middle somewhere. I am going to see someone who has an analyzer, but can you adjust the mixture at the tailpipe if you have a Cat? I don't think the folks I will visit have the port probe before the cat. Can someone she some light on adjusting the CO in a DIY friendly way? I have the Bently but it almost refers you to the dealer. |
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10-08-2004, 10:34 AM
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Designer King
Join Date: Mar 2004
Location: Toronto, ON Canada
Posts: 5,499
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Indigowhale,
You are doing what I have always done. With my car, if I keep the mixture a little shy of when the revs start to bounce when you come to a stop, or when the idle hunts when warm, then the mix seems right. I find I have to adjust this somewhat seasonally. Alternatively, some use a Gunson Gastester or have a shop w/ an analyzer do it. JW recommends 3.5% CO. There are also threads about raising and lowering the sensor plate by hand and seeing how the revs change to determine the correct CO.
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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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10-08-2004, 11:18 AM
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Virginia Rocks!
Join Date: Oct 2003
Location: Just outside the beltway
Posts: 8,497
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Quote:
 Read also this thread towards the bottom. I'm going to try Charlie's method as well. AFR meter or Gunson ??
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Rosewood 1983 911 SC Targa | Black 1990 944 S2 | White 1980 BMW R65 | Past: Crystal 1986 944 na Guards Red is for the Unoriginal
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10-08-2004, 11:38 AM
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Registered
Join Date: Aug 2004
Location: Northern Virginia
Posts: 437
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Thanks VASteve, the picture did not attach.
So I went by two service stations asking for a gas analysis and they looked at me as if I was crazy. Here in the very controlled state of VA, emissions is a bid deal and the machines are always in demmand--DIYers not welcomed. I am back to the manual method until I find a gas analyzer. The car was running so well after the AFM adjustment that I burned some rubber coming out of the station and hit close to 7K RPM with a hole lot of ease. Not a single complaint from the car and no hesitation or fuel cut-off. However there is some slight surging when driving easy so I suspect the manual adjustment is still way off, but what a difference that silly screw makes. VASteve are you in the northern area? What are you using to gauge your CO%? |
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10-08-2004, 04:05 PM
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Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,350
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Check out this web site ( www.systemsc.com ) on the Diagnostics page and the
section on Poor Running. The AFM must be adjusted internally to properly affect the CO value over the full RPM range versus just the screw for an idle CO setting.
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Have Fun Loren Systems Consulting Automotive Electronics '88 911 3.2 '04 GSXR1000 '01 Ducati 996 '03 BMW BCR - Gone |
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10-08-2004, 08:30 PM
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Join Date: Aug 2004
Location: Northern Virginia
Posts: 437
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Looked at that link, but not sure about opening up the AFM again. It was not easy.
I finally lost the allen wrench after several magnet recoveries in the engine's black hole trying to adkust mixture, so I can't mess with it anymore. Does anyone make a tool for this? and is there a tailpipe analyzer that is reasonably priced for the DIY? If I can't do it myself it is going to the wrech. My wobbly idle still persists, instead of being a purring kitten is a galloping horse. I've turned screws in every direction along with several others on this board to no avail. Even put in a new HTS today. Any help welcomed. Indigowhale 
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10-09-2004, 07:21 PM
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Join Date: Dec 1999
Location: Novato, CA
Posts: 4,740
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The "galloping horse" idle can be corrected by reducing the amount of bypass air on the throttle valve in order to reduce the base idle speed.
Joe |
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10-10-2004, 06:58 AM
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Go Speedracer, go!
Join Date: Aug 2002
Location: Indianapolis
Posts: 1,951
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Quote:
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1981 SC ROW Coupe |
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10-10-2004, 10:37 AM
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1976 Porsche 914 2.0L
