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Registered
Join Date: Dec 2001
Location: Cordova, TN
Posts: 1,222
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Air Fuel Mixture Guage
As recomended I bought a Air fuel guage. What should it read. Mine fluctuates from lean to rich. Then when I accelerate it goes all the way lean. It catches up as the speed levels off and goes from rich to lean. When I let off the gas it goes slightly rich. I am sorting out some problems and I am sure this is not right, but I was wondering what the guage should read.
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Roger Hall 81 924 N/A Some people are like Slinkies. Not really good for anything, but you still can't help but smile when you see one tumble down the stairs. |
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04-06-2003, 06:46 PM
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Join Date: Jan 2003
Location: Idaho Falls, ID
Posts: 1,199
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Roger, fluctuating from rich to lean under cruise conditions is normal and necessary for the catalytic converter to operate properly. When you accelerate, it should go to the rich side 700-900mv under full throttle. It sounds like you have a lean problem under accel but proper mixture/operation at cruise.
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75 914 - Undecided. 80 931 - Gone, but not forgotten. 72 914 - old toy- sold. And a whole bunch of German scrap metal shaped like 924's. Old enough to know better, and stupid enough to do it anyway! |
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04-06-2003, 07:12 PM
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Join Date: Dec 2001
Location: Cordova, TN
Posts: 1,222
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Thanks
I figured it should fluctuate since the O2 sensor is attempting to lean the mixture. I have a problem with bad input to my frequency valve. Im pretty sure its a wireing issue. Maybe a bad TPS also.
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Roger Hall 81 924 N/A Some people are like Slinkies. Not really good for anything, but you still can't help but smile when you see one tumble down the stairs. |
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04-06-2003, 07:20 PM
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Registered
Join Date: Aug 2000
Location: North Carolina
Posts: 302
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Roger,
I just sold my 1982 924 and have a lot of expierence adjusting the CIS system. What you are seing in called 'dithering' which is running 'closed loop' and the O2 signal is having the computer adjust the fuel mix back and forth. When full throttle, you should go rich. Make sure your full throttle switch on the throttle body is working. There were 3 switches on mine, 2 at idle and 1 WFO. Do you know how to adjust the idle mixture??? This will effect fuel delivery across the board somewhat. Heres a good place to go for more info http://www.924.org/contents.htm
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1988 951 Alpine White / Burgandy Profec B spec II EBC,HomeBrew Chips, WideFire HG, Tial 38mm, Magnecor Wires, Koni Rears, Adj Rear Droplinks, Zeitronix WideBand. |
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04-07-2003, 10:13 AM
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Registered
Join Date: Dec 2001
Location: Cordova, TN
Posts: 1,222
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Thanks for the link. I spend alot of time at 924.ORG. Yes I know how to adjust the A/F mixture. Here are some of the things I have done:
New air filter, fuel filter, cold strart valve, WUR, injectors. Swaped out used parts to rebuild fuel dist, and AMFU. Replaced ECU with used one. Rebuilt fuel dist with used parts from an AUDI 4000. Cleaned all grounds and connections. Three TPS switches all checked with continuity meeter ok. I never checked adjustment and voltage though. Here is what I think: Frequency valve fluctuates because of the dissimilar input check this post Sensor Question The signal to the freq valve is bad, and the A/F guage spends too much time in the lean range. Next is either the wiring or adjustments on the TPS or the RPM module. I have another used RPM module I will install it after I check the wiring for continuity and voltage. New fuel filter I belive there is more than one problem
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Roger Hall 81 924 N/A Some people are like Slinkies. Not really good for anything, but you still can't help but smile when you see one tumble down the stairs. Last edited by Roger Hall; 04-07-2003 at 01:52 PM.. |
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04-07-2003, 01:13 PM
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