east302
Full Access Member
The upper intake can stay on and should since the MPFI injector instructions say not to unclip them once installed. Seems like a dumb design for those things.
Random questions that have come to mind…
Are we sure that there isn’t a vacuum leak? Your heater hose water valve solenoid’s vacuum line is intact all the way to the PCV fitting? Plug it at the PCV fitting if it is. The little breather hose coming from the passenger valve cover to the air intake is connected?
If you put it in gear, brake and bring the revs up, does any particular cylinder misfire count spike? Some of those cylinder counts could well be reactions to the adjacent cylinder in the firing order misbehaving.
Is it your gaskets? An external leak would help, but if they’re 11+ years old then it’s reasonable. I doubt that they are original and if they are then that’s a problem. Two styles of gaskets are available so there’s no telling what was used when they were last replaced: the non-reinforced GM style and a more-recent reinforced version that should last longer.
Random questions that have come to mind…
Are we sure that there isn’t a vacuum leak? Your heater hose water valve solenoid’s vacuum line is intact all the way to the PCV fitting? Plug it at the PCV fitting if it is. The little breather hose coming from the passenger valve cover to the air intake is connected?
If you put it in gear, brake and bring the revs up, does any particular cylinder misfire count spike? Some of those cylinder counts could well be reactions to the adjacent cylinder in the firing order misbehaving.
Is it your gaskets? An external leak would help, but if they’re 11+ years old then it’s reasonable. I doubt that they are original and if they are then that’s a problem. Two styles of gaskets are available so there’s no telling what was used when they were last replaced: the non-reinforced GM style and a more-recent reinforced version that should last longer.