I have a problem with my 94 Suburban that has 116000 miles on it. I
cant get it to pass emissions, my hc are high at an idle and I have
noticed a miss at idle and so I replace the plugs, wires, cap/roter,
timing is dead on as well as replaced the fuel filter. But the miss is
still there, any thought on my small problem.
Try and pin down which cylinder, if it is a dead miss, short one plug out at
a time, the cylinder that does not change the idle speed is the culprit,
that is the starting point, high hc's is raw fuel entering the exhaust
stream from the non functioning cylinder/s. Lots of things can cause a rough
idle such as a vacuum leaks at the base of the TB or a bad egr, but if this
is a dead miss, start as I pointed out. Make sure the wires are in order and
you did not crack a plug putting them in, inspect the old plugs to see
evidence of a misfire.
pull your o2 sensors and clean them if they are dirty. also check you
coolant temp sensor. if it reads incorrectly to the cold side your pcm
will adjust the fuel ratio to the rich side to help with cold starting or
so it might think. probably would not hurt to clean injectors with a
solvent like b-12 chemtool made by berryman. see if that helps.
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