I just got a 1995 F-150 5L V8 with manual trans. When I am driving it will go fine but when I step on the clutch and let off the gas to shift gears the engine revs up to 2200-2500rpm and stays there for 10+ seconds before it starts to come down. When I let off the clutch and the engine re-engages the rpms drop back down. This only happens when I am driving. If I am stopped and rev up engine then let off the gas it drops right back down. I also noticed today that after I let the truck idle when I warm it up the engine throbs and cause the tach and battery guage to bounce. not sure if that is related problem or a whole different trouble.


Please help with any suggestion or thoughts.

 

Sounds like the IAC is sticking. Read this.



It's not for your symptom, but it's still related. It could also cause the tach/voltage surging at idle.

Clean & tighten your battery terminals.