Hello everyone.

I have a 1994 F150 XLT 5.8L 351 2wd automatic with 215,000 miles.

Some background on the truck , it sat for at least a year in an ocean town.
The truck did not run when i bought it.

I dropped the gas tank and cleaned it with a steel brush and scotch pads using a shop vac i sucked out the build up from scrubbing. It had a quarter inch build up in some places there were black chunks from sitting , the build up was yellowish brown it took hours but i got it clean and replaced the fuel pump and have replaced the fuel filter 6 times since then.

The truck has a rough idle the whole engine vibrates aggressively. When i put the truck in gear , the vibration gets slightly worse (the entire cab shakes).
when i accelerate from 1-30 mph the shaking goes away it comes back at around 30-40 mph except the entire cab shakes worse than the previously mentioned vibrations. If i let off the gas pedal the shaking stops , If i push the gas pedal in about 60-70% the engine revs up and clears the vibration. if I maintain the vibrations and tap the brake just enough to turn on the brake lights while staying on the gas pedal the vibration stops for about 1 second.

Things i have tried/replaces to fix this problem.
1) fuel filter changes (6 times , fuel filter was clogged each time)
2) transmission fluid (mercon used , shudder additive used) change , filter change (i drained the torque converter).
3) i replaced the ignition coil , distributor , rotor , plugs and wires (checked twice for proper firing order).
4) o2 sensor , map sensor and a couple other sensors a few months ago.
5) replaced four ball joints , replaced ujoint in driveline (other one had a zerk just greased it)

please help me ive spent a lot of money and time to no avail. =(

 

I'd buy a new tank, they aren't that much. If FF has clogged that many times the existing tank must not be clean. Go to that point and if it still has problems look at rest of fuel system, lines and injectors.

 

Yep, also check your fuel pressure regulator.

 

If you cleaned it that well you could be ok. As said check the f/p regulator - that's the big round thing on the fuel rail - pull the vacuum line off and check for fuel smell - there shouldn't be any. I would guess considering the bad fuel issue that you may have some clogged injectors (where you say it shakes is about where it shifts - lower rpm) so you can try running some injector cleaner through, just dump some in to a full tank.
You can also do a compression check - that would tell you if the problem is internal, but I'm guessing injectors. If cleaner in the tank won't do it you may have to change or remove and clean them.
But do a fuel pressure check first - new pumps don't always work the way they should.