[Diy_efi] O2 Sensor or Computer

[Peter Foote]

Hello;

Here's a strange one I've been fighting for a while but it showed up
perfectly tonight. I was driving my car with a throttle body '747
conversion. The O2 sensor was giving a good signal and the computer was
self-learning. The integrator values had mostly returned to 128 and the
block learn values were mostly above 128. It was running really well.
Perfect, I thought.

Then I stopped for gas! After that, the block learn values all began to drop
to 125, which is the min. value I allowed. The O2 sensor was constantly
reading high and causing the computer to "de-tune" the motor so lean it
wouldn't run right. It's done this cycle a few times and really has me
puzzled.

I have a 1-wire O2 at the collector in the exaust but it does read right
some of the time so I don't think it needs to be heated. It's behind ceramic
coated headers and they seem to really hold the heat in. Also, I had a meter
connected to the O2 sensor and it was reading the same high numbers the
computer was. This makes me think it's the O2 sensor. Anyone ever see an O2
sensor ntermittently work?

Can the computer back drive the O2 sensor? Anyone have any partial
schematics of the O2 input section for that computer? I probably have to buy
parts either way and would like to replace the right one.

Peter


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