It is practically unheard to fix a problem with a Chrysler product by replacing the fuel filter on a gas engine.
The first thing to do is run a new wire from the battery negative cable to the engine block. If that solves the shifting problem, you can try cleaning the ground connection on the block, but chances are the cable is corroded inside the insulation. Logic says it should not crank with this condition, but that's not always the case. If that added ground wire solves the problem, replace the negative cable.
Since you did a good job of noticing and providing additional clues, if the cable doesn't help, try a different throttle position sensor and MAP sensor next. I assume you did not see the "Check Engine" light come on while driving.
Once you install a new throttle position sensor, you will need to perform the minimum throttle relearn procedure so the engine computer will know when it has to be in control of idle speed. Drive the truck at highway speed, then coast for at least seven seconds without touching the brake or gas pedals.
The transmission looks at readings from the two sensors to determine shift points and harshness. Normally, a glitch in either one will be detected by the engine computer which will turn on the Check Engine light. An incorrect reading that is still within acceptable limits will cause issues, but won't set a fault code.
Another thing to look for is idle flare-up when starting the engine. Without touching the gas pedal, engine speed should go up to around 1500 rpm, then come down to about 800 rpm after two to four seconds. If it does, the engine computer is capable of controlling idle speed. Stalling at idle would be in response to a sensor reading.
If there is no idle flare-up, the air passage around the throttle blade is plugged with carbon or the idle speed motor isn't working. It's a stepper motor with four coils of wire that are pulsed with voltages from the engine computer. Problems with this circuit commonly cause stalling when you pull up to a stop sign, or the need to hold the gas pedal down 1/4" for the engine to start.
Wednesday, March 25th, 2009 AT 10:05 PM