MarcusM

1999 Mustang GT. Recently had a headgasket go so we replaced it. Everything appeared to be ok once we were done however at idle in DRIVE it won't stay running. In Neutral it will idle a little low and rough. When driving it will be fine, just surges if you stay at a constant speed. When I slow down to a stop sign in drive it will eventually die, so I have to put it in Neutral to where it barely stays running. The Mass air flow is clean. The injectors are all spraying. The coils are all firing. New plugs, gapped correctly and firing. I thought it was a vacuum leak, when I checked all the hoses and listened with a tube I couldn't find anything. Even put hose clamps on almost every vacuum line?!?! So I'm down to maybe the IAC? Is that possible that the IAC would make it surge at high RPM too?

MarcusM

Anyone?