I have a 2005 gmc envoy 4.2L and have changed coil # 5 for misfire code po305 also changed spark plugs,and removed and cleaned throtel body and reset pcm.car runs great except at idel you can feel a misfire without any code showing up. can anyone help?
Please help! Misfire at idle?
- Thread starter CHUCK
- Start date
Welcome! Did you use Delco 41-103 plugs?
When you say a "misfire" can you be more precise? Does the idle go up and down every few seconds? Or is it a vibration only that's steady and doesn't show up in the tachometer? Is the vibration different or does it go away if you put the shifter in neutral as compared to drive?
When you say a "misfire" can you be more precise? Does the idle go up and down every few seconds? Or is it a vibration only that's steady and doesn't show up in the tachometer? Is the vibration different or does it go away if you put the shifter in neutral as compared to drive?
Yes i did use delco 41-103 iridium plugs.
it runs great when driving with no misire or loss of power.
when i stop it has a slight thump when ideling every 5 or 10 seconds.
the idel is at 600 rpm and you can see the tac drop ever so slightly when it has the misfire.
it runs great when driving with no misire or loss of power.
when i stop it has a slight thump when ideling every 5 or 10 seconds.
the idel is at 600 rpm and you can see the tac drop ever so slightly when it has the misfire.
Mystery misfires can be injector-related, in which case Seafoam often helps. Or CPAS-related, in which case an oil change or a new CPAS often helps.