I have a 1990 f150 straight 6 that has been bucking and jerking like crazy after it has warmed up a bit.When I giver throttle it momentarily clears,but then starts to buck again.(its almost like I'm driving slowly in too high a gear,or punching the gas on and off).I had it in a Ford dealership and they could'nt pinpoint the problem but suspect the main processer.When the map?? sensor line is unplugged and blocked the problem goes away,but of course idles terribly and keeps flooding.The o2 sensor was replaced but made no difference.Anyone out there have any experience with this type of problem?

 

I know i'm asking a question you can't answer but what did they expect to prove by disconnecting the MAP sensor?
It controls main fuel to the engine and would certainly have great effect on how the engine idles.
The better thing to do to test it would be to apply vacuum to the Map with a hand pump, in place of the engine vacuum and vary it to see if it controls the fuel, the way it is supposed to and or sub it with another one.
The Map is a vacuum to AC signal converter which the computer translates to fuel needed for engine load. It's signal is in the 145 hertz range and varies with vacuum applied.
There is fuel pressure to check and ignition performance to start with.
Don't know what to tell you if they won't go out of their way to make a better effort to discover what is happening.