Hey wats up. I got a '92 F-150 XLT 4x4 with the 5.0 and 5 speed. Its runnin the 3.55 axles, the borg-warner 2.56:1 t-case, with 31x10.50's but Im only gettin 5-6 miles to the gallon, city and maybe 7 highway. Worse yet the truck only puts out bout 175 horses. I recently did a full tune-up (plugs, wires, cap, rotor, oil change, air and fuel filter replacement) I even timed the damn thing, but it isnt making a difference for either of my two problems. I was wondering if anyone with the a similar truck was havin the same difficulties??

 

Sounds like you are driving a Semi, with eighteen wheels. That is horrible I hope someone can help you out. If they cannot, sell it. Buy something with all the gas money you will be saving.

 

have you ever replaced the oxygen sensors?

 

Sounds like you may have a clogged catalytic converter.. that can definitely cause mpg and power loss like you described.

 

Tell us how you went about timing the distributor setting.
And are the Ox sensors plugged in?
If you get the ignition timing set retarded, that will do it.
Un plugged Ox sensors runs the motor on rich fixed fuel tables.
Map sensor geting a low vaccum signal will run the motor rich.

 

Well i unplugged the SPOUT connector as they call it, and got it at 10 degrees before tdc like my haynes manual said, and then plugged it back in, basically just followed the proceedure that the book told me.

 

A new EGR valve helps big time on those models

 

Yeah i have thought of that but i wanna wait til spring when i get the exhaust replaced because the guy that had before me has it runnin 2" straight exhaust duals, with only a small cat on each pipe, which wont pass the PA inspection or emissions, but also the guy was a jack-*** and did the exhaust himself, and let me tell hes not a welder.

 

that sounds like part of your problem there. take the truck to a reputable shop and have them run two high flow cats, an x pipe, and a good muffler(s) such as magnaflow, as well as new piping.

 

sounds like 02 sensors or clogged cats. could try some Seafoam through the combustion system.

 

i have a bigger motor than you and i still get better MPG, i get at least 12.

 

How many miles on the engine?

Does it even have compression on all 8 cylinders?

O2 sensors, as mentioned, will NOT cause this kind of issue as the computer has programmed values to rely on IF they were faulty.

The engine isn't burning fuel somehow and a dead cylinder will do that.

My 4 cylinder Ranger did this kind of stuff before I dumped it last summer. Crummy gas mileage, no zip from a stop, #4 cylinder down for the count.

 

Well it only has 117k, n yes i did have a compression test done n the lowest cylinder's compression was about 85% of the highest cylinder.