Bugzee8

Just bought a 1995 manual with 70000 miles. Put $20 of premium texaco gas in it and it developed a miss. Passed it off as bad gas due to no SES light. Ran It down to empty and filled car back up. Didn't not miss for whole day then started missing again and blowing black smoke. Done the paper clip test and gave 2 O2 sensor codes. Could the O2 sensor make it miss and blow black smoke?? Further more the SES light comes on now and stays on for a little while and then goes off. The car also don't miss all the time just sometime. It's really got me super confused. Any ideas would be much appreciated. First time posted and also AWSOME site here. This is we're i found the paper clip test also. Thanks again!!

Paul Workman

I had that exact set of circumstances when I bought my 95 Vette. Same symptoms, including the intermittentcy. And, it turned out to be a bad O2 sensor. It would sometimes run fine, and then run rough and blow black smoke from one pipe, and wouldn't always throw an SES light, unless it had been missing for a while. I left it with the shop for a week and got it back, "no problem found". But, before I got home, it started missing and laving a black trail.

I ended up buying a scanner and hooked it up to that ALDL connector and kept the unit running and handy until the problem occurred. When it did, I pressed the "EVENT" button which recorded all the sensor readings at that moment, and the sensor readings preceding and after the "event". The right bank O2s would short out (voltage dropped to zero) and the ECM saw it as a lean condition and doubled the injector dwell time on the right bank injectors!

I don't know if your situation is the same, but black smoke = excessive fuel, and the fact that you sometimes don't get a code and then, after a while, you get an SES light...is uncanny. For sure you would want to have it scanned and pay attention to the O2 voltage AND injector dwell time.

OR! You might have an injector that is sticking open. That would cause an issue too. A fuel pressure leak down test would shed some light on that. (Get back to us with more findings, soon as ya can.)

Bugzee8

Thanks Paul. I'm going to try o2 sensor first and see what happens. I'll keep y'all posted. Thanks again for the info.

Bugzee8

Well took car to pep boys and put it on scanner. Show same codes as paper clip test. Passenger side exhaust had black smoke coming out while at idle also. Changed the O2 sensor on passenger side pre cat and fixed problem. All is well for now. Lol.

Paul Workman

Glad it worked out.