I have a 1994 F150 300 cubic inch 6 cylinder fuel injected. It runs good till you put it into a strain like when you start off. The engine misses and once you get up to speed and drop it into 4th or even 5th the engine spits and jumps. You can let up on the gas and it will stop, when you go up a hill the same thing happens! Sometimes you have to drop back to a lower gear.
I have changed the fuel filter and checked the timing and it looks ok.
If I understand your letter correctly when you’re sitting still the engine runs well. When you put it in gear and put a load on it will miss.
This could be a bad spark plug wire or spark plug. It could even be some more sinister such as a dirty injectors.
Please have a professional test drive the truck to verify the problem. I suspect it is not serious and may be just needs maintenance and a "tune up".
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