My '93 5.0, 106K miles, is giving me a hard one to figure out. No KOEO codes are set, and the engine running codes it is displaying are 536,538 and 632, so no issue there . It is acting as if there is a force of resistance against it, most noticeably when pressure is released from the gas pedal, and moreso at higher speed. It accelerates OK, runs smoothly, but just seems to want to give up momentum too quickly after easing up off the gas. Also, when going up inclines, it also too soon jumps down into lower gear in order to get up the grade (even with foot on pedal, not in cruise).

I suspect the Throttle Position Sensor, and did a check on it (replaced it previously at 64k miles for similar symptoms). TPS did not come back with the in range values, neither with ko (0.0 v) or with engine running. But I am doubting those results b/c no ( 12#) code is set on it. Is it possible the TPS is bad even with no code?

Coincidentally, I just completed replacing all rear brake lines and new shoes on the rear wheels, and all seems well there, nothing dragging, so I don't suspect the issue is the braking system. I did the front brakes a few months ago.

Appreciate any thoughts.........

 

632= overdrive cancel switch not changing states. The transmission may be sticking in overdrive. When in overdrive the lockup torque converter locks in. If the converter doesn't unlock then you will feel these types of symptoms.

My first thought was sticking brakes so raise the truck and check them, particularly the front. The calipers have a tendency to stick after a brake change from compressing them in to install the new pads.

 

It sounds like your brakes are dragging. You won't get too many codes with an OBD1 system as it doesn't monitor very much. However if it isn't the brakes the few codes you got may give you an indication of what is wrong. Before doing anything disconnect your negative battery cable for a half hour and then pull the codes again.

But like I said I would check the brakes first.