I am starting to have some drive ability trouble. When driving down the highway if i try to acelerate the truck will start missing/shaking. When I first start the truck all is fine for about 5 to 10 minutes. I have tuned up the engine, new plugs, wires, pickup coil, ignition modual, fuel pump, fuel filter, MAP sensor and VSS sensor. Any help would be great.

 

On my '85 F150, 302 EFI I've recently experienced a similar situation -- bucking and misfiring, eventually leading to not being able to run above idle. After a lot of code reading and time and money wasted replacing sensors, it turned out to be a blocked catalytic converter. On my truck, there are two catalytics, connected in series. It seems the front unit let go and contaminated the rear converter which, in effect, blocked the entire exhaust system.

You could check this by connecting a vacuum gage to the intake manifold, downstream of the throttle valve. If you have a low vacuum reading (anything under 18"), at idle, disconnecting the exhaust pipe from the header(s), wedge a block of wood or something to separate the pipe from the headers and see if there is any improvement in the way the engine performs. It will make a racket! Any improvement in the way the truck runs, suggests a blocked exhaust system.

You could also experience similar misfiring with defective high tension ignition wires, distributor cap that is tracking, a corroded rotor and fouled spark plugs. If your high tension wires are old or you have a lot of miles on them, it may be something to look at. Easily seen in a very dark setting, with the engine running. It will show sparks jumping (tracking) to ground not unlike twinkling stars. Be careful not to run the engine without proper exhaust ventilation - it could take you out!

Good luck with your diagnostics.