1986 Pontiac Firebird Starts Up, then high idle, then low I

MRDENNIS87

MEMBER
1986 PONTIAC FIREBIRD

Engine Mechanical problem
1986 Pontiac Firebird V8 Two Wheel Drive Automatic 112k miles

It Starts up right away, I replaced spark plugs last year, when it starts up it seems to ile really low for about 30 seconds, then it will idle really high for 30 sec's then really low 30 sec's n repeats. Most of the time it will stall right back out as soon as its started, then I start it back up and it stays running. And drives fine. Just when I first start it. It stalls. Everytime I start it, it does the idle thing, runs lil rough when low idle of course.

1 Reply

ERNEST CLARK

MECHANIC
1,730 POSTS

This sound like either a vacuum leak or fuel related issue. Check all lines under hood. Replace any that are suspect.

Then check fuel filter and your fuel system pressure. This'll give you fuel pump operation and see if there's any leaks in the regulator or injectors.

If pressure is low, suspect the pump. If pressure is normal, shut off the motor and see if the pressure stays the same. If it does, the regulator/injectors are NOT leaking. If pressure drops, then something is leaking.

You can also pull the vacuum line on the regulator and smell/look for fuel. If there's any, then the regulator is leaking.