my car has been miss fireing alot but for some reason the number 7 cylinder has misfired about 5 times as much as any other.....i have changed the plugs coils wires and injectors and yet it still does this......could this be a valve train problem??when the car is reved up past 3800 it stops misfireing and revs up perfectly....any input would be great...

 

This could also be a MAF problem or an O2 sensor problem. Do you have a K&N filter? i had trouble with my car acting stupid b/c I used too much oil on the filter when I recharged it and it got on the MAF. Try cleaning your MAF carefully. Also, when your O2 sensors go out, it can cause your car to act stupid until you get up in the RPMs and it will straighten out.

 

Sounds stupid/simple...but last time I saw a car with that code, it also smoothed out over 3k or so...it had a bad spark plug. I would assume it would be the first thing you checked when you had a misfire...just making sure.

 

i have changed plugs,wires,coils,and injectors.......it is just kinda wierd that number 7 mis fires way more then any other cylinder...we checked the spark on number 7 2day and even with a new coil and everything the spark is real weak...instead of being a blue color the spark was more yellow.....maybe a wire comin from the computer is causing this???i also do have o2 sims and wut nont but how would a o2 sensor only cause one certain cylinder to mis fire?? i'm stumped...please help!!!

 

Well good luck finding the problem, I am at the same situatioan as yours , and I replaced all u said above + mass air,O2`s,PCM, checked Harness and finally checked vacum leaks.

I guess I will be lookin on the valvetrain very soon.

 

if you have O2 sims on the rear sensors you are ok, but you cannot run O2 sims on the front sensors. the car will not run right b/c the computer actually reads off the front sensors to control alot of things. unless you go speed density and delete the front O2's you have to have them plugged in.