QuestionQUESTION: 1994 Chevrolet 1500 pickup.excessive Carbon is coming from my tailpipe, whats causing it.
ANSWER: Hey,
The EGR valve sticking in the retracted position would be themost likely cause. O2 sensor, MAP sensor, plugged PCV. There are lots of things that cause excessive carbon but the marjority of them are the EGR valve. How is it running?
Wayne
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QUESTION: It seems to be running pretty good and I would not have noticed so much carbon except you could really see it in the snow. Thanks for giving me a place to start, with the help of my Chevy Truck repair Manual I think I can fix the cause. The manual doesn't troubleshoot problems of this nature and I have to rely on good ol mechanic know how from good people like yourself.
Bob
AnswerThree things that contribute to a rich air fuel mixture on that vehicle could be
A the oxygen sensor
B Map sensor
C Vacuum leak
An oxygen sensor that is stuck lean with command the ECA to continually add increments of fuel percentage over time until it gets to is maximum fuel adaptation
A faulty map sensor or vacuum leak to sensor will make the computer incorrectly calculate base and power enrichment of the fuel injectors
A vacuum leak will accentuate the map sensors ability to miss calculate base pulse width of the injectors.
02 sensors do not last forever. According to most specifications in those years about 100k was about all you would get out of one. An oxygen sensor should cycle between .3 and .7 of a volt bare minimum.
Wayne
