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F250 Towing Problem

I have a 1995 F250 SuperDuty pickup with a 5.8L FI Engine and an automatic Transmission with Overdrive. The truck runs great except when I am towing a trailer up a grade. When I start the grade climb after a few minutes, the Check Engine Light starts blinking and then stays On, and the power drops off drastically. Sometimes I am just going 30 mph up the grade. Doesn’t matter if I am towing a 1500 Lb or a 6000 LB trailer, the behavior is the same. I might mention that when I am towing I turn OFF the overdrive via the button on the end of the transmission shifter. When I reach the summit, of if I am going downhill, or on flat ground the Check Engine light goes OFF and power returns. I understand that the 1995 F250’s computer does not store codes, so I am up the creek on this one. I don’t know how I can simulate the condition at a mechanics shop. Anyone have a solution to this problem???

Here’s how you pull the codes on your 95 F250 and their definitions.


Some 1995 model year vehicles were already OBD2-compliant

I wonder if this is one . . .

If so, there will be a D-shaped 16-pin diagnostic link connector in the cab, usually under the dash, on the left side

It sounds as if you have a severe misfire . . . a flashing check engine light tends to indicate that

That would explain why you have diminished power, at those times the check engine light is flashing

Is this truck due . . . or overdue . . . for an ignition tuneup?

Have you ever tried turning off the O/D when you are not towing, to see if a problem occurs then?

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I’d be surprised if that’s the case. Your truck is electronic fuel injected, right? That engine configuration almost always has a diagnostic code facility. Assuming you can’t read them yourself using the tips above, you may have trouble finding a shop who knows how to read the codes from that vintage. But a Ford dealership would know how. In any event, that’s the best place to start.

In the absence of any diagnostic codes, you’re most likely looking at some kind of ignition system problem. The lowest cost way to fix this is probably to bring all the routine engine maintenance that’s behind up to date first, spark plugs, distributor cap and ignition rotor, spark plug wires (if equipped), engine air filter, fuel filter, then go from there, checking

  • crank position sensor (if equipped)
  • ignition module
  • coil or coil packs

Still not solved? Check compression and fuel rail pressure.

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Sounds like fuel starvation under load to me.