I have a 1994 Ford F150 Supercab with a 300 inline 6 and automatic transmission. I had been having a vibration upon slight acceleration when going up a hill and had a slight vibration at normal cruising speeds. I had the ujoints replaced and that has cleared up the vibration.
However, when I took the truck for a test drive immediately after the ujoints being replaced it cruises great at speeds below 30 mph but will not accelerate past 30 mph. When I hit the gas nothing happens, it doesn't spit or sputter it just seems to die out. If I let off the gas and give it a slight amount of gas it will run alright til I get up to 30 mph then does the same thing. It seems like it is starving for fuel, but it doesn't completely stall out, it seems to still be running just has no power to accelerate past 30 mph.
Does this sound like a bad fuel pump or a clogged fuel filter? It will idle fine and rev's up when in park or neutral normally but if I put the brake on and put it in gear and load it up it starts to stall once a load is on it.
Thanks for the suggestions. I actually had some time to test it out after work last night and found that it would go up to 50 but barely, then I turned and it wouldn't do 20. I started to suspect bad gas as it was at 1/4 of a tank. I swerved the truck back and forth and it ran a bit better. I put some more gas in it and it works fine now. I don't think the truck was driven much before I got it so I think there is some junk at the bottom of the tank.