I have a 93 F250 with the 7.3 IDI NA motor and an E40D transmission.

Sometimes when the truck goes to shift out of overdrive it will rev up real high for 1/2 a second before going into gear. This typically happens between 40-55mph and when I am going up a hill. I have noticed that the motor will start to bog down a little bit before this happens (sound changes from the normal roar to a dull thudding and I get a small black cloud out the tail pipe).

I already put in a new tach sensor and adjusted the TPS. The OD light does not flash, and I have not noticed any other codes coming up. The OD light did flash before replacing the tach sensor.

Thanks in advance!

 

See if there are any codes stored.

http://www.troublecodes.net/ford/

 

Looks like it is tossing a 23. Which if I am not mistaken is the TPS is out of range? I had a mechanic check that and checked it myself. Maybe it changed. I will recheck it when it is not raining. Any other thoughts to consider?

 

Did you hold the accelerator pedal on the floor when running the key on engine off test?

 

No, I was not aware that I should do that. I am assuming that changes the effect on the TPS?

 

Yes, and it sets a code if you don't hold the accelerator down while running the test.

 

Yup, now it is a 67. So it is either the Park/Neutral circuit or it is the Manual Lever Position circuit. I have never done either before, any idea which is either more likely/better to try first? Looks like they are actually the same thing? Or am I missing something?

 

I've seen that code set if the AC is turned on when the test is running. Or if the trans wasn't in park.

The park/neutral circuit is part of the MLPS. They are the same thing.

 

The truck was in park and the A/C is turned completely off. Any other quirks that I should consider?

 

During the engine running test you need to press the brake pedal, press the OD OFF button, and turn the steering wheel about a quarter turn.

But I think you have a problem with either the MLPS or the wiring to the MLPS.

 

Sorry I quit responding. I had a bunch of stuff come up that put this on the back burner for the past month. I did not see any other codes when I followed your procedure and went ahead with putting a sensor in this evening. I took the truck for a drive on some hills that always make it freak out, and it worked magnificently.

That said, the solution was the MLPS. Now, if I can get the miss out of the motor that showed up 2 weeks ago....

Thanks for all your help! Hopefully, your responses can help some others too!