I am new to this forum and it is also the first forum i have joined. I recently bought a 1994 F150 4wd. When i got it it was hard to start but seemed to run ok. After driving it for awhile it started cutting out and the throttle seemed to have dead spots (no matter how much i pushed the pedal it never seemed to accelerate). Now the truck wont go for more then a few blocks and it cuts out and almost dies unless i turn it off and back on real fast, then it runs ok for a few more blocks. It seems to be back firing out of the intake. It also takes forever to start i have to hold the pedal to the floor for about 15 seconds while cranking before it starts up. It is also shifting very hard and idleing odly. So far i have replaced plugs, wires, cap, fuel filter, and cleaned the maf sensor. I have read that this could be a throttle position sensor? Any help would be greatly appreciated.

 

The routine maint. items you replaced are a good start. I believe the TPS is also a good move.

 

i have a parts truck that only has 115,000 miles on it i took the tps off that truck and put it on my truck and it still does the same thing, takes forever to start and cuts out after driving only a few blocks. could it be a leaking intake gasket or a o2 sensor?

 

check catalytic converter and look for obstruction in exhaust

 

There are two things that we check when experiencing problems like your vehicle seems to have. The first is , are you getting spark to fire up the engine when hard to start?
The second is , are you getting fuel? You have to be getting fuel at the proper pressure or it won't start or run. What we do is spray some carb and choke cleaner into the intake and see if that helps it to start. If it does, we continue checking out the fuel system from the pump in the tank , the fuel filter , then right up to the fuel pressure tap on the fuel rail. If you have a fuel problem that will help locate it's cause.
If you have an intermittent spark problem, that can get more involved, but at least you have some idea which direction to persue.

 

no cats and straight pipe. Would not having cats make it run terrible?

 

For what it's worth,
94 was an OBDI system.
Do you get a check engine lite?
No cats , I don't think so , but a defective oxygen sensor could influence running quality.
See if you can get any codes from the ECM.

 

just installed a new o2 sensor and a new coil. (the coil was sparking when the wire was off of it.) now it is starting like it should but it still seems to be doggy. I checked the fuel pressure at the rail. With the truck off and the key turned to the on position it read 20 psi with the truck running it bounced between 30-32 psi. Im not sure what it is supposed to run at. any ideas?

 

give me the engine you have and I should be able to come up with the pressure readings

 

it is the 5.0L