Hey guys, hope you can help me out. I have a 93 f250 351 auto with 1.5 dual exhaust and 31x10.5 tires. The truck is seriously lacking power when on the highway. It constantly kicks in and out of overdrive to maintain speed. If I'm driving into a wind it cannot hold 60-65 on flat ground without downshifting out of OD. What I've done so far is plugs, wires, cap, rotor, air filter, fuel filter. Also checked compression and it only has a 8 psi different across the motor. Any help will be greatly appreciated. Let me know if there is any info needed that I left out. Thnx!

 

Welcome to FTE!

I would assume you have an E4OD transmission. I assume you have 3.55 gearing. I do know that my wife's 2000 Expedition with the 5.4 and 3.55 or 3.73 gears with same trans or 4r70w does the same. Also, my 302, .40 over, 31-255-5 Comp Cam, 3.55 gearing and AOD trans does the same. I have same tires as you and my tires are larger than the Expedition.

All in all, it sounds about right. I always keep the truck and Expedition in "D" when there is large amount of headwind.

May not be the best answer, but it seems normal. Hopefully other members will share their thoughts.

 

Maybe it is just fine and I'm overreacting, but I find it somewhat hard to believe. I've had 2 other trucks of this generation and I also have a bronco and none of them are dogs like this one is. Any slight incline and it loses mph as if I've let off the gas. If the answer is to not use OD the I'll be doing around 2500 rim just to do 60....

 

1.5" exhaust.. really? Or is that a typo? Does the truck still have the stock cats?
No your trucks should not be that gutless so something is wrong.
What is the timing set to?
What is the fuel pressure?

 

A lot depends on if you know everything about the vehicle. And you said compression test is good on all cylinders. New exhaust, so that takes care of notoriously clogged cats. Fuel psi to spec? Rear drums perhaps dragging a bit? Have you checked for stored codes?

Just some more ideas.

I saw the 1.5 exhaust, but I think it's a typo too. That would be a large bottleneck.

 

My bad, it is a typo. It's 2.5 in true duals, with no cats and it is new exhaust. The truck is somewhat new to me, so I do not know everything about it. It does not have any codes right now. I will check fuel pressure and timing and get back to you guys. Thnx

 

How do you know? Did you check for codes then receive a system pass?

Or are you assuming there are none since the Check Engine Light is not on?

The latter is a false assumption.

 

You are correct, I assumed it had none since the light isn't on. I did not know that... I will look into it. Thnx

 

An all too common urban myth...check for codes!

Start with the Key On Engine Off tests and Continuous Memory (Stored) display.

 

Alright I read the codes and got 3 of them. 114, 116, and 636. With a Google search it looks like
114 - IAT sensor out of range
116 - Engine coolant sensor out of range
636 - Trans oil temp out of range.
Can anyone confirm that I got that correct? Thnx.

 

Were those codes retrieved with Engine cold? If so, then those are correct. Warm the engine up, or drive a few miles, and then perform the test again.

A side note though, it doesn't appear to show any other codes except those.

 

Yes the motor was cold when I did that. I will let it warm up and do it again. Also I check fuel pressure and it is around 35psi

 

Ok, I let the truck get up to normal temp, shut it down and checked for codes again. This time I get 111, which means no codes correct??

 

The 10.50,s are part of the problem. They are keeping it out of the proper rpm, so it,s hunting the biggest downfalls of autos. The answer is keep it out of overdrive when pulling. Even a headwind is going to be considered "pulling" when the engine/Trans is trying to work in the correct rpm.

 

Code 111 is system pass.