Problem gradually building for a while. Cannot isolate any components Threw codes for Fuel pump secondary circuit,Throttle position sensor out of range,And egr. All these systems check out O.K. Truck runs smooth some days and then it's like a switch is thrown and it starts missing and sputtering all over again.

 

I just fixed mine which was missing under light load and at idle. One of the plug wires was bad. I installed a new set and all is well again.

 

Sounds like the tp sensor is taking a dump if there is a code set. That sensor alone can cause your problems. You can check it with a voltmeter. Turn the key to on, pierce the green wire going into the tp sensor. It should read about 0.9 volts at closed throttle. Slowly open the throttle while watching the voltage. It should smoothly increase to almost 5 volts. The problem with the tp sensor is that it is usually at about the same position during driving and will wear its contacts at that point. Replacing it requires removal of the throttlebody and turning it over. Hint, tap on the screws that hold it on with a hammer before attempting to remove them. A little rust penetrant wouldn't hurt, either. They tend to get stuck in the aluminum.

Robbie

 

Thankx for the input. A little more info, didn't want to start with a story.Problem existed before a new long block. Has got increasingly worse Low power always , on bad days it feels like it is running on 5 cyls.V8! New plugs, wires ,cap and button new coil and the t.p. checks out O.K. Fuel pressure steady 40PSI. Im leaning towards a pcm problem but don't want to purchase to troubleshoot. Any other ideas are appreaciated.