1999 pontiac montana miss

[Wade S]

just changed intake gaskets (fel pro # ms98003t),runs good no coolant leaks but after it warms up has a miss at only at idle. ran vaccum test and put code scanner on it but everything within specs and no codes?? any ideas as to what would cause this?when its missing you can rev the motor and it doesnt even hesitate and doesnt miss a beat going down the road?

 

[baldie]

there must still be a vacuum leak somewhere. spray some starting fluid around all fittings.

 

[bandit]

It sounds like there is a gap in the graphite core of one of the plug wires.
New wire should do it. Buy the longest one and change one cylinder at a time until you isolate the cylinder.

 

[pc_renaud]

mine was doing the same , turns out the head gasket was leaking into #1 cylinder causing it to misfire, hope this isn't your problem