I know, it's not a Camaro, but hey, i need to keep my daily driver running in order to afford to keep my Camaro looking nice!

I have a 1991 Nissan Pathfinder with 111k miles, V6 engine. When the car runs fine, it purrs like a kitten. No smoke out back or anything like that.

Anyway, the problem is an irratic one. Once in a while the rpm's go way down and then shoot way up. Recently was idling so poorly it almost would stall at stop lights. Black smoke was coming out back also.

I pulled the plugs and all 6 of them were completely covering in black soot. Not wet, like oil, but i suppose carbon.

I cleaned the plugs up and the car runs just fine again. I'm pretty stumped, cause everything seems to be in order and running well, and then out of the blue, this happens.

I thought maybe the O2 sensor or idle mixture, but just not sure...
I believe these cars are computer controlled and dont need mixture adjustment.....

PLEASE HELP!

thanks in advance,
mike




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My '69 Camaro Convertible (http://www.geocities.com/TelevisionCity/Screen/1243/Camaro3-1.html)

Check the coolant temp sensor..It may be speratically sending a "cold" signal to the ECU, therefore causing a rich mode by added more fuel..when it starts running poorly, disconnect the coolant temp sensor ECT, NOT the sensor for the gauge, this will put the ECU into a preset average temp reading, and the rich mixture should go away, if so, replace the sensor..this is somewhat of a common problem on Jap engines.


Gary

thanks gary, ill give it a shot. I checked the codes on the computer and it shows a "55" , which means normal operation. That puzzles me a bit.....

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My '69 Camaro Convertible (http://www.geocities.com/TelevisionCity/Screen/1243/Camaro3-1.html)

If you haven't changed the oxygen sensor in awhile, could be the problem. I believe they're good for 60k. When mine went bad, the rpms would surge and dip and it would cut out at stoplights.