Long story short I have a '91 Ford ranger with the 4.0 and auto trans. It is on its second engine and trans since I have had it and has always ran reasonably well aside from hole I put in the first block.

It has recently started stalling when in gear and throttle is applied, like pulling out of a parking lot or from a stop light. If you ride it with both feet and keep on the gas slightly it will not stall. When the vehicle is in neutral or park and you push on the accelerator to increase the rpms instead of it revving up it will either stall completely or stall out and then the rpms pick back up.

The plugs, wires, coil pack, map sensor, maf, iat, and tps were replaced with no effect what so ever. I even swapped out ecus with a known good one to no effect.

I did notice that if I unbolted the tps from the engine and left it plugged in to the harness the engine would run correctly. It just does not have any power above about 3500rpms as the tps is not signalling the computer to increase fuel or timing.

So my question is: What could possibly be the culprit of the strange behaviors of my truck? I have replaced about every possible engine control sensor other than the crank sensor and I'd imagine if it was bad it just wouldnt run.

I have checked all of the fuses, the engine bay wiring is in great shape, and the check engine light is NOT on. I am stumped.

Anyways, I appreciate any insight as to where my problem may lie.

 

Have your tried pulling codes?

 

Yes I have tried pulling codes. There are none other than the ecu self test code. 21 I think

 

I would try pulling any codes again and count the light blinks carefully. Code 21 is for the Engine Coolant Temp. sensor out of range. Also have you checked for vacuum leaks? Have you checked for plugged cat? Have you checked that the engine wiring harness is properly grounded? I`m no expert so just my thoughts. Good luck with it.