On 4 Feb 2005 11:43:46 -0800, "imsjry" > wrote:

>
>Lawrence Glickman wrote:
>> On 4 Feb 2005 09:20:56 -0800, "imsjry" > wrote:
>>
>> >Ok, here's the story. My service engine light came on and the car
>> >started hesitating when I would accelerate. Had a mechanic read the
>> >code and he said my pre-cat O2 sensor is shot. Replaced the part
>myself
>> >and drove about 120 miles the next day. Car was running great and no
>> >engine light. The next day I start the car and the engine light is
>back
>> >along with the sluggish performance. 72,000 miles on the car.
>> >
>> >Any ideas folks?? What would be causing the light to keep coming
>on?? I
>> >can't believe a brand new sensor would be the problem.
>> >
>> >Thanks in advance..
>>
>> You have to check for corrosion at the plugs in the wiring harness
>for
>> the O2 sensor, to be sure there isn't any.
>>
>> You may also want to take the "new" O2 sensor out and inspect it for
>> fouling. If it is fouled, you have another different problem that is
>> going to continue fouling your O2 sensors. The sooner you know about
>> that the better.
>>
>> Next, maybe you should monitor that O2 sensor to be sure the voltages
>> are going hi and lo enough. Should go up to zero point 9 volts, and
>> drop to zero point 1, at a pretty good rate of speed ( every few
>> seconds ) on a running engine.
>>
>> For some reason you're not getting the correct voltages to the PCM in
>> the right time intervals to keep from throwing an O2 DTC code. It
>> -could- be something in the exhaust manifold fouling the sensor, that
>> is why you want to pull it and inspect it for fouling. If it is
>> covered with crud, suspect a head gasket problem or similar.
>>
>> Lg
>
>Thanks. I will pull it out and check it. What am I looking for exactly
>with "fouling"?? Am I just seeing if it has turned black or looks
>clogged?

Sure. It should be _clean_, as in, the temperatures in the exhaust
manifold where O2 sensor is located should reach up to 1,500Farenheit.
That would normally burn-off anything except the most egregious kind
of crud being spewed from the engine. If you see gunk, crud on your
"new" sensor, there is something leaking into the exhaust manifold
that is depositing that crud, either from the cylinders or from a
leaking head gasket.

As I said, at those temperatures, the O2 sensor should be -clean-.
Were it not so, they would all foul and have to be replaced weekly if
not daily.

Lg