Thread: Random Misfire

My 98 Grand Prix GTP has been having misfires, it has given codes P0300, P0305, P0303. The main code that comes up it on cylinder #5. what happens is when driving or at idle the car with start to putt and die. when driving and this happens the check engine light flashs and a great loss of power happens, and you can smell fuel just running through the car without being burnt. Once i stop the car and either it dies or i turn it off after an unknow period of time it have it give it full throttle to get it started again but once started giving it some gas seems to clear it up. this problem comes and goes....?

have you changed the plugs/ wires lately?

I have changed the plus, wires, and fuel pressure regulator

The problem misfire can happen after a few days from the last one or i have even had it go almost two months before the next issue. I have taken it to the dealership to have them check it out and they said they had no idea but it a history scan of the codes and seen that it has misfired on almost all the cylinder. there was a lot of misfire too. cylinder 6 was the only one with out any and cylinder 5 the main code that it throws when the issue happens had just over 12,000 misfires. yes thousand.

What type of spark plug did you install? Platinum, copper or irridium? How do the terminal posts look on the coil packs? Nice and clean? Maybe start up the car and start jiggling some wire harnesses to see if you can make it stumble. Check out the wires harness to cyl 5. Also check the harness that connects to the ICM (the thing that all the coil packs bolt onto).

Platinum plugs and all the terminal posts look clean on the coil packs, as do the wires going to cylinder 5. I will try jiggling some harnesses. I have heard the fuel pump resistors go bad on these engines would that make it throw a code?