rodneyhall

1989 F150 5.8L with 3 speed automatic, 2 wheel drive.

Torque and horsepower lethargic for an engine this size. Takes a heavy foot to speed up from stop (sucking gas along the way) and seems to struggle getting up to 70mph. It's also getting a consistent 8.5 mpg no matter what I do (driving habit, gas additive, etc.). I can tolerate low mileage but not if it comes with low performance. Suggestions on what to investigate? Thinking it might be a fuel delivery issue given the bad mileage or possibly tranny related. Any suggestions:

Here's what's been done in recent months:

New plugs, wires, distributer cap, fuel filter and reset to factory specifications. New water pump and radiator flush. Transmission service (fluid and flush). Gas additive every other fill-up.

dirtcrew51m

How many miles? Did you have the injectors cleaned? Was it always sluggish? You also have to remember thanks to the brain dead enviro feds there is maybe only about 60% actual petroleum in gas, the rest is gas wasting crap such as up to 20% methanol, so everyone's mileage and power is affected. Especially the larger engines, they are more affected with the lack of petro in gas.

ymeski56

What's that mean?

Did that work effect performance?

rodneyhall

Dirtcrew51m: mileage is 96,000. I've had it for six months now and it's always been performance handicapped since I bought it. Have not had the injectors cleaned nor the fuel pressure checked. Understand how the gas quality would effect performance but in this case, it seems like it is still way underperforming for an engine that size.

ymeski56: I assume reset to factory specs meant timing and EFI adjustments.

Thanks for the replies. I'm open to any suggestions.

Mr.Distance

My 90 can -almost- put me in my seat at speed, with a 5.0 that has a cracked manifold and a miss depending on its mood. My mileage is horrid though, probably because I'm 16 and should have a 2x4 under my go-juice pedal... but. Ima go ahead and suggest away. seafoam(let it sit for a decent while, I'll suggest...), lucas injector cleaner unless its been used as an aforementioned additive... and, honestly, drive the HELL out of it when you've got extra gas money.

I gave it a bit of insanity on the highway to work, then across a field. The next morning, going to school, I was on a decent uphill, figured, "eh, she sounds loud, might be struggling, bit more gas..." and she picked up and WENT, put me in my seat, uphill, and took me to 70 from 45 pretty quick.

ymeski56

Seafoam alway's helps, but it would be good to know what kind of compression #'s your getting. Only way to know if you're trying to beat a dead horse or in fact you are having issues.

wde3477

Is the diminished HP something new? Otherwise, the stock 5.8L was rated for only 210hp @ 3800 rpm and 315 lb-ft torque at 2800 rpm in 1989. Thank the feds for getting the emission regulations ahead of the available technology of the time.

Was the SPOUT connector removed when setting the base timing?

Does the cat show signs of being plugged / restricted? An engine is nothing more than a glorified internally-fueled air pump - any airflow restriction on the intake or exhaust is a problem.

ymeski56

good points!

rodneyhall

How would I know if the cat was clogged. Replace muffler last year and completed a state inspection earlier this year.

Not familiar with the spout connector. Will research and check it out too.

Thanks everyone for the suggestions.

Tiderfish

Also check the fuel pump, or if you have 2 tanks, check both. I have read of a lot of problems when these die.