O2 Sensor and fuel consumption
 

My '86 Carrera has been getting lousy mileage recently.
It had to be leaned out to get thru smog in CA.
Even after this, it's slurping too much gas.

Could it be caused by a faulty (or worn out) 02 sensor?
(I say faulty because the mechanic said that the mixture
changed on the way to the testing station).

Could you post the smog results? It might be helpful in diagnosing the problem.

craigyirush,
I do not know about the Carrera's but an inoperative O2 sensor on my SC resulted in a huge decline in mileage. After reconnecting the 'loop', my mileage increased 22.8% (15,000 mile baseline).

Thanks for your responses.

I forgot to bring the smog report to the office. Will post it tomorrow.

But my question is not about the numbers - I passed smog - but about whether the O2 sensor can have an intermittent fault causing the mixture to vary?

I may just replace it as a precaution as I don't think the previous owner had done so for a while.

Don't have access to a scanner.

Smog numbers (first reading at 15mph and 1508 rpm; second at 25mph and 1728 rpm):

%CO: 14.2/14.6
%O2: .4/.4

HC: 97/50

CO%: .79/.19

NO: 502/447

However, since I passed (and my mechanics leaned out the mixture to get the pass), I am STILL getting lousy fuel economy.

My question: could this be the 02 sensor working intermittently? Have any of you had this happen - the car running too rich right after a mixture adjustment?