1996 Ford Mustang hissing sound and low rough idle

96BLUESTANG

MEMBER
1996 FORD MUSTANG

Engine Performance problem
1996 Ford Mustang V8 Two Wheel Drive Manual

notice a hissing sound and low rough idle and when the a/c is turn on the idle goes up when the a/c clutch kicks on and goes back down when turn off. I have replaced the IAC valve and clean M.A.C. Ran ok for a day then went back to rough idle. Checked all hoses and sprayed carb cleaner and found no increase in idle around vaccum hoses. But did spray around head gasket and throttle both sides. But (top) passenger side area toward front the idle did go up as I sprayed that area! I think I have found the problem bad head gasket. Notice no oil in coolant and no odd color in motor oil. Just need to know that the head gasket is bad giving the reason the idle is rough? Do not want to keep buying parts that are not needed.

2 Replies

BMRFIXIT

MECHANIC
19,053 POSTS

What is more common is the intake manifold gasket
and in that case no coolant or oil would leak just a suction sound as a vacuum leak
which it is

1.Disconnect negative battery cable. Release fuel pressure, and disconnect fuel lines.
Remove engine compartment brace.
2.Remove air cleaner outlet tube. Remove accessory drive belt. Remove ignition wire covers. Remove ignition wires. Remove alternator and mounting bracket. Disconnect control cables from throttle body. Disconnect necessary vacuum and electrical connectors.
3.Disconnect upper radiator hose at water by-pass tube. Remove water by-pass tube. Remove EGR valve. Remove upper intake manifold retaining bolts in reverse order of tightening sequence. Remove upper intake manifold.
4.Disconnect fuel injector harness connectors. Remove lower intake manifold retaining bolts in reverse order of tightening sequence. Remove lower intake manifold.