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Discussion Starter #1
Does anyone know why I have carbon fouled spark plugs, a glowing cat cov and my s3 does not respond well to acceleration. It seems that it has no power when I press the accelerator and shortly after it regains the RPMs.

Please note I removed the Cat Con....but the symptoms are the same on plugs and accelerator.

Any clue?


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If a Bosch cars is crudding up the plugs, usually it means it's burning some oil. Have you monitored? Is it high miles? Have you done a compression test?
Could also I guess be an ignition system issue, but that's more of a works/doesn't work issue.

Andrew
 

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S3 Fouled plugs

check the voltage signal at the O2 sensor (at the connector).The voltage should read between 0-1 volt.The voltage should switch regulary with .45 being stoichmetric. O2 sensors can fail in any number of ways, including being shorted to power voltage(12v.).
 

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Do you have the correct heat range plugs? Cold plugs will foul in a clean engine if it is not run hard enough. I would try a new set of NGK BPR6ES.
 

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But Mad North-Northwest
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Glowing cat is a rich mixture. You've most likely either got a miss on one cylinder or a bad oxygen sensor.

The glowing cat was a symptom, not the problem. Removing it was not a fix.
 

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Discussion Starter #11
Gubi,

I agree with you.. do you know how to test the Oxygen Sensor. Perhaps it is easy to replace it... but I have hard time removing it from the Cat.

Any suggestion on removing (Oxygen Sens.)??
 

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Soak it repeatedly with penetrating oil and use an oxygen sensor wrench which you can buy at an Auto parts store, Harbor Freight, Sears, etc

After you have removed it you can test it by holding the tip of the probe in a propane flame while you measure the voltage between the signal wire - probably black and the metal case. It should be about .5 volts and it will vary as you move it in and out of the flame.
 

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Does a bad O2 sensor cause the car to run rich mixture for an S3??
Yes. The fail safe mode for Bosch FI is rich. It may stop the engine from running properly but it will not damage anything.
 
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