Revs at Startup

[JonnieBlue]

What causes this difference?
Sometimes when i start my car in the morning - 86 xt coupe MPFI - it will
either do one of two things.. sometimes it will start and rev aroun 900, and
overall seem to preform sub-par. other times, it will start and rev at 2 or
2.2k and run better.. sometimes ill start it, it revs normal (2-2.2k), park
at the store, and when i come out and start it it revs low(900 or less)...
what causes this and how do i fix it??

JB

 

[JonnieBlue]

Anybody have suggestions??

 

[JaySee]

What causes this difference?
Sometimes when i start my car in the morning - 86 xt coupe MPFI - it will
either do one of two things.. sometimes it will start and rev aroun 900, and
overall seem to preform sub-par. other times, it will start and rev at 2 or
2.2k and run better.. sometimes ill start it, it revs normal (2-2.2k), park
at the store, and when i come out and start it it revs low(900 or less)...
what causes this and how do i fix it??

JB

This is the function of the Idle Control Valve.
Your car is supposed to idle higher when the engine is cold to warm it
up. Getting closer to operating temperature, the idle gradually drops
down to eventually 900 RPM. You can adjust the valve to idle higher,
but it just wastes gas.