Truck Lunges and has a Rough Idle


#1

I recently Bought a 1989 Ford F150 4x4 and when the truck is stopped or in idle it wants to lunge forward. The battery gauge jumps back and forth as well. The truck has a fairly new battery. I have replaced the spark plugs/wires/dist. cap/ and rotor button and this did not help. The truck runs great down the road and will run good for a while after stopped but then starts the rough idle after a few seconds. Any Ideas??


#2

Have a look at one of these:

Intake air (vacuum) leak
faulty fuel pump
Faulty IAC (Idle Air Control) motor.
Or perhaps an emissions fault.