I have a 1984 Ford F150 pickup truck with the 4.9 litre 6 cylinder gas engine
and a 4 speed transmission
. we bought it brand new and it has been a dandy. sometimes, after the engine warms up, i put it into gear, press the accelerator and the truck will go to a certain speed and then start bucking and trying to throttle down, if i continue to "put my foot" into the accelerator, it will increase speed and then do the same thing. I shift gears and it will do the same thing, reach a certain speed and then start this jerky motion. Most of the time, after it has been driven for a little while, and is running at operating temperature, it will quit and the truck runs smooth like silk.
it hasn't been tuned up in years, i am going to do plugs, wires, dist cap, rotor, ignition module this weekend and set timing.
the truck has 158,000 miles on it but still passes emissions. I have been thinking that the catylitic converter and muffler could be plugged up, they are original equipment. what do you think??