1995 F250 w/351W.
no CEL, No OBD I codes (111 no errors KOEO & KOER)
Idle surges between 500 & 700 rpm.
When engine is cold and early in the Morning the idle surge is barely noticeable. However as engine heats up and the day gets warmer the
Idle surge is very noticeable.
Replaced EGR and TPS sensor, new IAC valve. new PCV
New plugs, MSD distributor cap and coil.
Replace all those brittle plastic vacuum lines w/color coded neoprene vacuum
lines. Engine has great acceleration.
However this idle surge is puzzling.
Any Thoughts and/or ideas would be greatly appreciated.

Thanks
Guy

 

Coolant temperature sensor.

 

coolant temperature sensor?! Hmmm Thanks I'll look into that possibilty

 

Turns out I had a loose spark plug wire was not making a good connection
so the number 2 cylinder was running rough.

 

Thanks for the reply back with the root cause and resolution.