okay i have a very annoying problem with my 96 crew cab 4x4 dually. it has 240,000 Km on it and runs and starts excellent however it has a very erratic throttle and seem to be all over the place. usually on the highway it will idle up like its dropping into 3rd gear and if you put your foot to the floor it will go back into overdrive. pulling a trailer or up hill it is fine. if i plug it in to a tech 2 scanner it has a code for APPS Sensor or wiring and fuel cutoff time too slow. another thing is when you let off the throttle it sometime takes a few seconds before the rpms drop. i havent changed the fuel filter since i bought the truck and i know it does need it but i havent got around to it. pmd has been relocated to an aluminum bracket on top of the intake. i thought it was the transmission before and had it changed to a different but still used transmission out of a parts truck. the dropping out of overdrive problem seemed to go away for a while and then returned and the erratic throttle was the same. it has the same issue in overdrive on the highway and seems to have an issue negotiating downhill slopes. it will start to cut the fuel off like it should and then it bucks and surges all over the place and sometime it will get so bad it will just turn the cruise off and i have to set cruise again..

any ideas ?

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forgot to mention i also put the apps pedal out of a parts truck in the truck and same issues

 

Has the smell of a PMD starting to go.......

Check the grounds for the PCM

Check the lift pump output.

Tech II should be able to identify APP 1, APP 2 or APP 3. There's three sensors in it for redundancy. There's "limp modes" when you start having APP problems. You're doesn't sound like APP limp modes.....

FYI; PMD mounted on a heat sink on the intake manifold -



- is worse than having it mounted on the injector pump.....you have to get it right out of the engine bay.

Ironically, you'd be better off to leave it on the pump where the fuel passing though the pump body can strip heat away.

 

99% of the time its only the APPS if check engine light for it

 

thanks guys. i kind of thought that as well and i have asked a local shop if i could borrow one of there spare pmds just to see if the symptoms changed. i have checked the grounds at the back of the head and cleaned them up. there is also a ground strap under the passenger side that i think runs from the frame to one of the tranny bolts or the starter that i remember being either broke right off or in really bad shape when we did the tranny.

 

update. i tried a brand new pmd that a local shop let me borrow and nothing changed.

 

so there is a code for a APPS?