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Old 05-05-2008, 05:19 AM   #4
91Caprice9c1
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Location: Long Beach, California
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Re: O2 Sensor and Fuel Filter Where Are They?

Quote:
Originally Posted by mr.Hand
is there also another o2 sensor after the cat converter?
Yes, pre-cat is for fuel trim and post-cat is for monitoring catalytic converter performance only.

Quote:
Originally Posted by mr.Hand
and when you buy one do you have to get the one that has the plug adapter, or can you just buy the one with the wires. I guess you have to put a plug adapter on yourself, cuz that one is much cheaper. The OEM one is 77 dollars.
You don't have to buy OEM, aftermarket will work fine. You just have to pay attention to color codes.

Quote:
Originally Posted by mr.Hand
i think that i may have too lean a fuel mixture, because i am seeing lots of carbon all over the tailpipe and on the back of the car. it could also be due to the engines age as well, it has 180,000 miles on it.
A lean mix will not do that, a rich one may. Perform a compression test, check your fuel pressure, and back-probe a Digital Volt/Ohm Meter to the blue o2 sensor wire (for four wire sensors) and ground to chassis or B-. After the engine is at operating temperature, the voltage should oscillate regularly between 0.1 and 0.9, should not go negative, and should not stay the same.

I think you'll probably find a low dry compression figure that increases with a wet re-test, indicating worn piston rings. You may also have a leaky injector.

-MechanicMatt
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1996 Caprice 9c1 - Daily Driven Project Car

1993 Geo Metro - Accident

1991 Caprice 9c1 - Destroyed

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