My '85 does that, too, and sets an 02 code, then it goes away.
On the '81, I don't have the info that specifically says what sets that code....is it running rich, lean, or is it not getting a signal at all? Don't know. I do have the Service manual at home, tho, so I can check into it later, unless someone else can first. I do know it will
only set while driving at hiway speeds for at least 5 minutes...
Could be an 02 sensor that is lazy(not responding quick enough), might have some carbon build up on it, but could also be a wiring problem right at the sensor. Chances are a new sensor will correct the problem, as long as the fuel mixture while cruizing is within limits. The problems you've had with your fuel pressure situation is prolly also causing this code to set.....
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Joel Adams
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