skybowd15

Hey, This is my first time posting to this forum but I have always found really helpful information on here, but my misfire is driving me nuts. I have a 2007 Grand Prix GXP with around 170k miles. It recently started misfiring. I had the code checked and it showed a cylinder 4 misfire. I replaced the plugs and wires all within the last year, so I changed the coil. Problem was still there so I changed the injector. Still misfiring. The only thing left I can think of would be a wiring issue to the injector or coil. I haven't had time to check that out yet though. There is some damage to the right front speed sensor wiring that causes the speedometer to fritz occasionally but that just recently started as well. I plan on fixing that soon as well. Is there a possibility that they are related? From what I understand it shouldn't but with all the electronics and DOD I could be wrong. Any ideas on what it could be? Thanks.

rottonj

iTrader: (4)

Just because the plugs and wires were recently replaced doesn't mean they can't be the problem. Check the resistance on that wire and swap the plug to see if the code moves to another cylinder.

skybowd15

Thanks! I will definitely look into it. Im a full time student and work so time is definitely hard to spare at times. Today I checked the resistance of the old wires they were around 1.3kohms and the new wires are around 300 ohms and I checked multiple wires. Im assuming you would get more voltage with less resistance and less current I'm not sure which actually creates the spark so is the lower resistance better or worse?. I changed the coil over to a different cylinder and the misfire stayed on that cylinder. I put a new sparkplug in right after I put on the new coil. But the new sparkplug didn't look very new to me so I could have gotten a bad return or something. I'm just hoping it's not a bad cylinder. Could it be related to the computer or intake system or would that affect all of the cylinders?

rottonj

iTrader: (4)

In theory a wire with less resistance is better, having all wires within the same range is important as well. What brand wire did you use? An intake vacuum leak could also cause a misfire,at some point if you are still having a misfire a compression test will be needed to compare cylinders. Good luck

06MonteSS

AC Delco or NGK are the best plugs and wires to use, period. also, make sure your coils are good - again, stock AC Delco are the best to use for coils...

also, get a can of CRC Mass Airflow Sensor Cleaner and clean your MAF sensor... and make sure you reinstall it facing the correct direction - the arrow on it should be pointing towards the throttle body/engine...