High idle help

[josh_m]

My trucks idle seems to be stuck around 2500 - 3000 rpm. REally annoying. It started happening after i got a TPS from the wrecker (My truck wouldnt go below 1500 before). I threw the new tps on, it stayed around 1500 rpm and i just drove it and didnt care. Recently, it wont go below 2500 rpm, and is usually around 3000. It was fine for like a week before that. I cleaned the throttle body and ensured that it closed all the way. I just cleaned my IAC out and am waiting a couple hours with the battery unplugged to see wat happens. At school today i ran codes and came out of it with these

Key on engine off : 63 (TPS low voltage)
Key on engine on : 98 (hard fault) and a 63 (tps low voltage)

So what on earth is a "hard fault"

For the record, i get around 12mpg driving very nicely around town, with some highway driving. is this normal ? Where should i look next ? thanks

 

[Otto]

I had the same problem with my 4.0

I had it taken to a mechanic and he replaced the intake gasket and its been idling fine sinse

 

[holyford86]

code 98 tells you to get a pass code in KOEO before running the KOER test, try replacing the TPS with one that is known to be good (test it) or just buy a new one. Make sure that the wiring to the tps is good as well.

 

[johndeeregarner]

Try the idle adjuster on the front of the TB. Just adjust it out and the engine should idle down. That happened to me and I did that and it fixed it.

 

[Psychopete]

The screw is not a direct idle adjustment, the computer controls the idle speed. The screw on the TB sets the base voltage for the TPS sensor. Adjusting it will only make it that much harder to diagnose the actual problem.

Pete

 

[Syko]

had this happen to me after trying to clean out the TB with some TB cleaner.. turns out a chunk of crap got stuck in the idle air bypass (i think thats what its called.. passenger side of the TB) anyway it was stuck open.. cleaned it out and all was good

 

[josh_m]

Turns out my cruise control cable was popping out of the housing and making my idle stay high. Snipped it and im good to go.