Hey All
I have been trying for the better part of 2 months now to
isolate a number 4 cylinder misfire with no luck. I have put new
plugs,wires and coils in with no help. I have changed the fuel
injector;no dice, misfire still present. Took the car to Pontiac
where a compression check passed. They had the car for
over 3 hours and could not pin anything down. Did mention that
the PCM driver circuit for number 4 fuel injector could be failing,
but they were not sure. Got a used PCM with the latest GM
software and still number 4 cylinder misfire. I have checked the
the wiring to the injector with a home made LED and ran this
inside the car. While the misfire is occuring the LED flashes
nomally, so it appears the driver circuit for the injector is intact.
Next tried hooking up the LED to the primary wires below the
number 4 coil pack, no problems here either when car is misfiring
the LED flashes normally. The hot wire to the injector is not breaking
down either as this was checked as well with a wire running inside the
car hooked up to multimeter. Meter showed 14 volts while misfire was
ocurring. The car has 112,000 miles on it and I am the original owner.
I thought perhaps knock sensors so I scanned the engine and here is
where things get interesting. At idle the scanner shows -22 degrees
ignition advance, does this make any sense. I scanned my fathers
2003 Caddy and got a reading of 9 degrees advance. How can my car
run at minus 22 degrees advance. Heres my question, is this a normal
reading for a car that is supercharged or are these readings way off which
I am inclined to believe. Appreciate any info you all are willing to part
with and sorry for being so long winded.
Thanks,
Steve
