I have and '87 F150, at take off, it starts to bog down like it is starving for gas. it also starts again when I hit between 80 - 100 kph. I have changed the fuel pumps, fuel filter, air filter, coil and cat. I have also checked the plugs and cap, and they are all fine. What else should I be looking at? i just it it scoped and it said everything is ok ? but the problem is still there and getting worse can anyone HELP me please

 

Few things you might consider. 1. Take a compression test. 2. Check engine vaccuum at idle. And 3. Check engine timing. These tests will help us determine the condition of the engine.

 

all came back ok

 

By 'scoped', I assume that you had the computer codes pulled? Does this 'starvation' continue at speeds over 100kph?

Suggest to verify the fuel pressure. Thinking about the possibility of a failed pressure/bypass regulator.

Was thinking of a throttle position sensor (TPS) problem - but that should have thrown a code, as should a failure of many of the other sensors like O2, EGR position, etc.

Assume that the timing was checked with the 'SPOUT' connector pulled?

Acceptable vacuum suggests that the cam timing is OK. Does the truck have a normal idle speed - if higher than normal, thinking of a vacuum leak somewhere.

Does the exhaust feel restricted? You've replaced the cat - but just wondering if anything else could be going on. My quick-n-dirty check is to feel the tailpipe at idle - if slight pulsing is felt, probably OK. If a steady flow is felt - may be worth investigating further.

 

yes it does it at higher speeds

 

and timming was ok

 

we just swapped out the computer and no change

 

Is there an known problem with a loud humming noise comming from the front fuel pump on the rail? I have noticed that when the noise is there the truck starts to bog down on me. I have changed the pump 3 times, and I still get the noise from the pump.

 

My pump is loud when it is trying to pump gas but there is none to pump. I run my truck out of gas a lot. There must be a hole in the line inside or outside the tank before the external fuel pump causing the pump to lose it's prime. The in tank pump may not be working well or the small gas reservoir on the frame rail may be leaking and emptying itself out, starving the external pump for fuel. There also may be a clog in a line.

 

i did what just call me sean said about the pump in the tank i changed it and put a new sock on it and it seams to be working fine thank you very much sean. elwayfan