OK finally drove my f150 after a rebuild (from a reputable builder) and am struggling to keep it at 55 on flat highway. Slows on hills n and struggles to stay near 55. This is a 1985 manual 4 x 4 f150 4.9 single feedback carb w/o cats new muffler system. My gas mileage is near 14.5 , Whats baffling it idles fine, runs great( no bucking engine missess) but just lacks the power and torque it once had.Down hills i can reach speeds of 65 but as stated climbing hills it slows to embarrassing speeds Any and all help woud be appreciated Thanks TR

 

Pull your computer codes, hopefully it thinks something is wrong that can be easily fixed.

Fuel Injection Technical Library » How To Run a Self-Test

 

Thanks , I do have access to a obd1reader TR

 

Check timing, check for vacuum leaks

 

A fresh rebuild is going to run tight until broke in.

 

Ok retriEved codes as following code 41, code 72 and code 73 , 73 Might of been my fault any comments. TR

 

All codes were under the koer, no cm codes Thanks TR

 

41 - system lean, fuel control
72 - No MAP or MAF change in "goose" test - retest, check for frequency or voltage change - MAP MAF
73 - (koeo test) Rerun test, if 73 is still output replace TPS (koer test)No Throttle Position Sensor (TPS) change in "goose" test Must get at least 25% throttle rotation - TPS

I am going to guess that it is running out of gas at speed. First thing would be to check the fuel filter and/or do a pump pressure and volume test.

 

Red after the rebuild a new fuel filter and fuel pump installed , i feel codes 72 and 73 were my fault. Now wondering it the new fuel pump (mechanica)l is bad TR

 

all else fails do a "coke bottle test". ground the coil and turn the truck over for a few seconds and see if it is pumping alot of fuel. If it fills the bottle pretty quick then it is not the pump. If it does not then it is either the pump or the pickup tube in the tank. On the old 63 ranchero I use to have the short rubber line from the tank to the fuel line started going bad and caused it to act up.

 

The gas tank has to vent properly too. If it won't vent, it'll cause a situation that puts the gas tank and fuel system under vacuum.

 

Ok , got rid of code #41, replaced the oxygen sensor, now the only code present is #44 in which my air pump has been previously removed for years .(koer)koeo is ok.Just dont under stand the power from this rebuild. It has been driven almost 800 miles since the rebuild.Any suggestions its all stock with the feedback carb.timing is correct and advances as it should fuel is ok , idles fine smoothe etc just seems weak all around TR

 

With the air filter off and engine not running, look down the throat of the carburetor and while someone else depresses the throttle, see if you are getting WOT?

Are the brakes dragging?

 

Checked the dragging brakes 1986,all good , will do the carb check (throat soon,maybe a float stuck not allowing fuel to provide a wot , if not maybe the gas tank has a suction as stated previously. Thanks TR

 

First of all , thanks to ctubutis, tinman52 ,harte3,redtires019,1983f150,1986f150six for your replys, i certainly appreciate them.The problem with the truck was simple.After getting help(someone to push the gas pedal) and tinkering with the accelerator cable it ACTUALLY would not let the carb have full throttle(wot)I bent my fork that the plastic acel. cable sits in towards the drivers side.Go figure this will go down as a lessons learned.Remember i, just had the engine over hauled after an honest 532000 miles.Seems maybe the fork was bent in the process .But anyway, the replys provided were helpfull (after looking at each reply). The line to my fuel tank(rubber ) needs replacing, also the tank vent line.As mentioned from ctubutis, i had to blow the dust off my obd1 and 2 reader(after locating it )Harte reminded me the engine is tight (still need to be easy)tinman 1983 and 1986 helped with the actual fix ,Thanks. think i will hang around the room a while , have been on here for years, in the bronco forum ---fyi, theres a guy in our bronco forum who has the keen knowledge of every system in our Ford trucks from emmisions to hardware (Greystreak) TR