Running rich
05-07-2002, 03:40 AM
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Running rich
Hi all-
My car exhaust has become kind of smelly lately. What would be the likely culprit of a overly rich fuel mixture? I thought the DME controls this. O2 sensor maybe?
TIA
Jon
My car exhaust has become kind of smelly lately. What would be the likely culprit of a overly rich fuel mixture? I thought the DME controls this. O2 sensor maybe?
TIA
Jon
05-07-2002, 06:07 AM
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Dear Jon,
The most likely culprit is the O2 sensor. If you are running rich all the time it means you are most likely in "open loop mode" all the time. Commonly this is caused by the internal heater in the O2 sensor failing. Did you have a situation before you noticed this of just one time it seemed to run badly but after the next start it seemed okay. If you did this suggests the O2 sensor. I would advise before actually changing the sensor that you check the wiring and the connectors in the circuit.
Ciao,
Adrian
911C4
The most likely culprit is the O2 sensor. If you are running rich all the time it means you are most likely in "open loop mode" all the time. Commonly this is caused by the internal heater in the O2 sensor failing. Did you have a situation before you noticed this of just one time it seemed to run badly but after the next start it seemed okay. If you did this suggests the O2 sensor. I would advise before actually changing the sensor that you check the wiring and the connectors in the circuit.
Ciao,
Adrian
911C4
05-08-2002, 01:39 AM
#3
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Jon, I can't remember whether you have a Catalytic Bypass or not? If you have one, that seems to be a new issue with my 964 since adding one...but then maybe I "bonked up" the O2 sensor?? I hope so, because I don't wanna give up my Bypass! <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />
The fumes are abnoxcious, and I'm noticing that when I pull up to stoplights, the decel of the engine produces a puff of smoke that is noxious to the drivers next to me.
It is not the type of smoke from an engine in need of a valve job either, it's a rich mixture for sure!
The fumes are abnoxcious, and I'm noticing that when I pull up to stoplights, the decel of the engine produces a puff of smoke that is noxious to the drivers next to me.
It is not the type of smoke from an engine in need of a valve job either, it's a rich mixture for sure!
05-08-2002, 02:02 AM
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Hi Jeff-
No I have the same old super-cata-fragilistic converter. I just remembered I have my emissions test from a couple of months or so ago. I passed, although I was kind of sweatin' it because I thought my car had a raw stank to it.. Here is my $15.00 dataset:
IDLE (882 RPM)
HC: 7 PPM (220 PPM limit)
CO: 0.07 % (1.20% limit)
CO+CO2: 15.14% (must be > 6.0%)
2643 RPM
HC: 18 PPM
CO: 0.02 %
CO+CO2: 14.94%
What does all this mean? In the words of PeeWee Herman...I DON"T KNOW!
No I have the same old super-cata-fragilistic converter. I just remembered I have my emissions test from a couple of months or so ago. I passed, although I was kind of sweatin' it because I thought my car had a raw stank to it.. Here is my $15.00 dataset:
IDLE (882 RPM)
HC: 7 PPM (220 PPM limit)
CO: 0.07 % (1.20% limit)
CO+CO2: 15.14% (must be > 6.0%)
2643 RPM
HC: 18 PPM
CO: 0.02 %
CO+CO2: 14.94%
What does all this mean? In the words of PeeWee Herman...I DON"T KNOW!
05-08-2002, 03:54 AM
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Dear Jon,
Passing emissions tests can actually be a bit of a red herring. I will tell you why. My daughter Stephanies 944 has no emissions controls and passes the emissions test with similar figures to my 911C4. A little worse but well within limits. O2 sensors can also be intermittant. I would certainly look at other things but I would advise you check out the O2 sensor. What you can do is a quick check. Disconnect it and see if anything changes.
The other issue which can cause running rich problems are the injectors. Maybe one or more is stuck open or a couple of internal gaskets have failed,
Ciao,
Adrian
911C4
Passing emissions tests can actually be a bit of a red herring. I will tell you why. My daughter Stephanies 944 has no emissions controls and passes the emissions test with similar figures to my 911C4. A little worse but well within limits. O2 sensors can also be intermittant. I would certainly look at other things but I would advise you check out the O2 sensor. What you can do is a quick check. Disconnect it and see if anything changes.
The other issue which can cause running rich problems are the injectors. Maybe one or more is stuck open or a couple of internal gaskets have failed,
Ciao,
Adrian
911C4
05-08-2002, 06:57 AM
#6
Dear Adrian
I'm very glad to reading you again.
Simply checking fault memory, via Bosch hammer or check engine light, isn't it enough to exclude O2 malfunctions ?
Are there O2 malfunctions not logged by autodiagnosis system ?
Thank you
I'm very glad to reading you again.
Simply checking fault memory, via Bosch hammer or check engine light, isn't it enough to exclude O2 malfunctions ?
Are there O2 malfunctions not logged by autodiagnosis system ?
Thank you
05-08-2002, 07:19 AM
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Dear Herbie,
The answer is Jein. Ja und Nein, yes and no. They should be logged but I know from experience that not always are they logged. Not everyone has the check engine light system or the same software status of DME. The earlier DMEs used primarily on the 1989 and 1990 964s are somewhat not very reliable when it comes to logging faults. It is also very easy to reset or clear the faults as well. The Bosch hammer is the most reliable way of checking but it is not perfect.
Ciao,
Adrian
911C4
The answer is Jein. Ja und Nein, yes and no. They should be logged but I know from experience that not always are they logged. Not everyone has the check engine light system or the same software status of DME. The earlier DMEs used primarily on the 1989 and 1990 964s are somewhat not very reliable when it comes to logging faults. It is also very easy to reset or clear the faults as well. The Bosch hammer is the most reliable way of checking but it is not perfect.
Ciao,
Adrian
911C4
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05-08-2002, 10:57 PM
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[quote]<strong>My car exhaust has become kind of smelly lately. What would be the likely culprit of a overly rich fuel mixture? I thought the DME controls this. O2 sensor maybe?</strong><hr></blockquote>
Sounds like you're building a case that a '91 Turbo really would be better
Sounds like you're building a case that a '91 Turbo really would be better
05-09-2002, 01:23 AM
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Ha Ha Very funny! 
No I've already talked myself out of that one due to my white 4x4 and the blue interior of the turbo. My car really is quite nice looking in my opinion and I looked for a long time until I found the one I wanted. I'm just a little frustrated at the moment.
No I've already talked myself out of that one due to my white 4x4 and the blue interior of the turbo. My car really is quite nice looking in my opinion and I looked for a long time until I found the one I wanted. I'm just a little frustrated at the moment.
