Check engine light keeps coming on for a cylinder 4 misfire. Cant figure out why. I have changed plugs, wires, injectors, fuel pump, fuel filter, thermostat.. but it is just this one cylinder.. and it only happens at idle, when i drive it around, it is good all around, doesnt even feel bumpy, but if i stop and idle for a while, THEN the check engine light comes on and i get the P0304 code and then a pending code for the same things.. "cylinder #4 misfire"
Mysterious Misfire
- Thread starter 99gmc99
- Start date
I have not. but wouldn't that effect all of they cylinders?
Molson02536
New member
There are no individual coils for each cylinder on the 4.3 vortec's. Common for cylinders to miss fire is the ignition system is running at 100% would be the fuel injector poppet valve dirty with carbon.
Try having your fuel injectors professionally clean first before trying to replace the poppet valve on your SCPI, but at that point. You might as well replace the system and do the upgrade to have it turning in to a MPFI system which is more reliable then the one that is in there now.
Good luck and keep us posted.
http://www.theautoshop.net/VortecMPFI.htm
There are no individual coils for each cylinder on the 4.3 vortec's. Common for cylinders to miss fire is the ignition system is running at 100% would be the fuel injector poppet valve dirty with carbon.
Try having your fuel injectors professionally clean first before trying to replace the poppet valve on your SCPI, but at that point. You might as well replace the system and do the upgrade to have it turning in to a MPFI system which is more reliable then the one that is in there now.
Good luck and keep us posted.
http://www.theautoshop.net/VortecMPFI.htm
Yeah, interestingly enough, i just replaced the fuel pump, filter, and upgraded to mpfi. it just randomly does this when it sits and idles for a while
already replaced injectors with the upgrade, thats why im confused.
and i just started having another issue. all of the sudden my brake light came on and i had a hard time stopping. well, i noticed i had a broken brake line that was leaking bad, so i figured it would be fine if i replaced it and bled the lines. well now i have little braking power and the pedel wont hold pressure. and when the car is on, if i press the brake pedal to the floor, it lets out the normal hiss, but the hiss will keep going. it doesn't stop and it is coming from the pedal area, just a constant hiss
and i just started having another issue. all of the sudden my brake light came on and i had a hard time stopping. well, i noticed i had a broken brake line that was leaking bad, so i figured it would be fine if i replaced it and bled the lines. well now i have little braking power and the pedel wont hold pressure. and when the car is on, if i press the brake pedal to the floor, it lets out the normal hiss, but the hiss will keep going. it doesn't stop and it is coming from the pedal area, just a constant hiss
alrighty got all of my issues fixed with brakes. Now back to this misfire. I have left the code alone and have observed that it goes off and on randomly. Cyl. 4 misfire. Only one cylinder. please, if anyone can help, im sick of 11 mpg!