Misfire cylinder three

02TRAILBLAZER1980

MEMBER
2002 CHEVROLET TRAILBLAZER
4.2L
6 CYL
4WD
AUTOMATIC
160,000 MILES

My vehicle shut off at a red light the other day. I started it back up and it was running real rough and the engine light was flashing. Had part store do diagnostic on it it said bad cam sensor. I replaced it that did not help. Diagnostic check again p0300 code came up. I replaced the cam positioning solenoid now shows code that cylinder three is misfiring any suggestions please?

1 Reply

CARADIODOC

MECHANIC
33,874 POSTS

First of all, the diagnostic fault code did not say to replace a part. They never do. Fault codes only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a part is referenced in a fault code, it is actually the cause of that code only about half of the time. First you have to rule out wiring and connector terminal problems.

A flashing Check Engine light indicates the most serious of conditions. Too much unburned fuel is going into the exhaust system where it will burn in the catalytic converter and damage it. You should stop the engine right away to avoid that damage.

Based on the mileage, with no other symptoms or history to analyze, the best suspect is worn spark plugs. Next would be a failing ignition coil. To identify that, swap two coils between the cylinder with the misfire code, and one other one. Erase the fault code, then see if a code sets for the cylinder you moved the suspect coil to. The clue this is a spark-related misfire is the flashing Check Engine light indicating there's too much unburned fuel.