i was riding around town and all was well today. i stopped at the store got back in started up ok and then i started to take off and in every gear when i switch gears(manual trans) it shutters and shakes until it gets over a certain RPM range and then goes away until i switch gears. it shutters as i press on the gas and if i gun it hard it feels like it wants to get all the power it can but it is held back until i get to that certain RPM range and then it all kicks in at once and then i have to shift again. i took it to pep boys and meinike for computer diagnostics and they found nothing. hey replaced the fuel filter and nothing. they checked the fuel pump and nothing. they cleaned off the mass air flow sensor and nothing. i added some fuel injector cleaner and that hasnt worked.i am taking the 99 ford f150 4.2l to the ford dealership on monday. i dont want to do this but this is the only option i have left unless anyone else has any suggestions.

 

You might need a tuneup - how many miles do you have on that thing?

Is your check engine light on? Maybe you're having some misfires.

Another thing that comes to mind is a bad spark plug or plug wire.

I know that a cracked motor mount can sometimes cause the shakes - have you hit a big a$$ pot hole lately?

I guess a failing and non-reporting oxygen sensor can cause almost the same thing. Intake and throttle body issues may also do something like that.

I'm just reaching now.