Hello- new here and a long post, so bear with me. 02 Yukon XL with 150K.
Came off a 20 minute freeway drive- at off ramp, started misfiring. Could feel the shaking, MIL flashing. Drove a mile and parked it. Restarted and it started just fine. Ran fine for a couple days. Did it again while driving on the streets. Shut down, restarts fine.
Took it to the shop- they said I needed plugs and wires. Done.
Took it home, ran fine for a day. Did it again.
Took it to the shop- no to very little fuel pressure. Replaced pump and FPR. (I knew the pump was dying a slow and painful death). Ran great for a day. Misfired again and got a solid MIL.
Took it to the shop- P0300 and a leak code. They said they did smoke test and tracked it own to a line of the evap valve. Fixed.
Now, I usually get the misfire at cold starts. It will either be P0300 or P0307. Coil has been replaced on Cyl 7.
Sometimes I will get a misfire in heavy stop and go traffic.
Sometimes I will get it after driving about 20 minutes (if it did not misfire at the cold start).
It does not always do it! The only time I can guarantee it to misfire is the second start after fueling up. Not right when I leave the station, but the first cold start after.
When it is misfiring, it will not stop until i shut down and restart.
It runs great 95% of the time!
I have replaced the fuel filter, cleaned the TB (on car), cleaned the MAF (about 4 times- could be me, but seems to run better after cleaning), replaced K&N with a paper filter, replaced main relay. Replacing the main relay helped my gas mileage, which was terrible.
I have run techron through the tank twice and seafoam once.
Everything i do seems to make a slight improvement.
Any help or ideas are greatly appreciated
Came off a 20 minute freeway drive- at off ramp, started misfiring. Could feel the shaking, MIL flashing. Drove a mile and parked it. Restarted and it started just fine. Ran fine for a couple days. Did it again while driving on the streets. Shut down, restarts fine.
Took it to the shop- they said I needed plugs and wires. Done.
Took it home, ran fine for a day. Did it again.
Took it to the shop- no to very little fuel pressure. Replaced pump and FPR. (I knew the pump was dying a slow and painful death). Ran great for a day. Misfired again and got a solid MIL.
Took it to the shop- P0300 and a leak code. They said they did smoke test and tracked it own to a line of the evap valve. Fixed.
Now, I usually get the misfire at cold starts. It will either be P0300 or P0307. Coil has been replaced on Cyl 7.
Sometimes I will get a misfire in heavy stop and go traffic.
Sometimes I will get it after driving about 20 minutes (if it did not misfire at the cold start).
It does not always do it! The only time I can guarantee it to misfire is the second start after fueling up. Not right when I leave the station, but the first cold start after.
When it is misfiring, it will not stop until i shut down and restart.
It runs great 95% of the time!
I have replaced the fuel filter, cleaned the TB (on car), cleaned the MAF (about 4 times- could be me, but seems to run better after cleaning), replaced K&N with a paper filter, replaced main relay. Replacing the main relay helped my gas mileage, which was terrible.
I have run techron through the tank twice and seafoam once.
Everything i do seems to make a slight improvement.
Any help or ideas are greatly appreciated
