To start its a 99 Dodge 2500 5.9l 24v with 370k on the odometer with an Edge with Attitude and an AirDog 2 165. Don't know if the 2 are related, but a couple days before the high idle issue started I noticed my WTS light stopped coming on when I turned the ignition on like it always used to. No CEL and checked codes and did't come up with anything. I drove down from Sacramento down to Vallejo and when I got there I noticed my idle was around 1100-1200 from the normal 850. Did what I had to do and drove back home hoping it would return to normal and it didn't. Again, checked for codes and didn't come up with anything. The weird thing is when I first fire it up it idles at the correct 850rpm, but as soon as I rev the motor over 1100 it stays there. The other weird thing is if I hold the brake and let the clutch out in gear and drop it back down to where idle is it will stay back at normal idle. It's only when I rev over 1100 it stays there. Did a bit of searching around but it's hard to find any info since apparently it's a common mod to make the high idle.

What I've done so far is take out and clean the IAT and reset the APPS. When I first turned it on the WTS light came on like normal, but again as soon as I rev'd over 1100 it stays there and then after I turned it off and back on the WTS light didn't come on anymore. Checked for vacuum leaks and I did find the silicone elbow off the nipple for my exhaust brake that goes to the rest of the vacuum lines was cracked so I replaced it and no change. All the other vacuum lines are all hard lines, and I checked all the silicone junctions and they all appear to be fine. I've had pretty bad vacuum leaks from the nipple before and it never changed the idle so I don't think its vacuum related.

Sorry for the long post, I just try to get as much info down as I can to help you guys help me . So far I've kinda determined it's either the APPS, IAT or the MAP, but like I said I haven't been able to find a whole lotta info on it so if any of you guys have any ideas before I go out and start spending money on new sensors that would be awesome!

 

first off: vacuum has absolutely nothing to do with how the engine runs. vacuum is created by the vacuum pump to run your 4x4 actuator, cruise control, and operate the hvac blend doors. The engine itself does not need or use vacuum.

next: the MAP sensor will have nothing to do with engine idle or WTS light coming on/off. the MAP sensor just tells the engine how much boost it has so it knows how much fuel it can/needs to inject to keep things in balance. So this will have nothing to do with idle.

APPS (accelerator pedal position sensor) is your most likely suspect here. A faulty apps can cause engine rpm to hang at a higher rpm.

IAT. this will control your WTS, but will have nothing to do with the engine idling higher unless high idle was enabled on your truck and it is giving an air intake reading of below 32*F..

also once the air intake temp is above 60*F the grid heaters will no longer come on during engine start and the WTS light will not shine because it is not necessary.

so if it doesn't come on after the engine is already warm, that is nothing to worry about.

if the engine is ice cold and the outside temp is below 60*F then it is time to worry about the IAT sensor.

APPS, vp44, or ECM are your likely suspects for the rpm hanging above 1200.

if you had a scanner or something that can give live APPS readings, that would help you better diagnose the problem to verify if the apps was acting up or not.

 

Well it has been getting down in the 50's for the last month so the IAT might just be bad. I was under the impression from what I've read from MoparMan that the WTS light will always come on even if just for a split second even if the truck is warm indicating it's working correctly, which is how it's worked since I bought the truck. I guess I'll just replace the IAT since I know I've at least put 20K miles on it since I got the truck and don't know if it's ever been replaced.

I have a feeling you might be right about the APPS though. When I first got the truck it had the deal pedal symptoms and I reset the APPS and it's been fine since, but I guess it time to just get one of those Timbo APPS.

Do you have any recommendations on a good scanner tool? I've got a basic one that just show the codes, but I'm willing at this point to go out and spend the money on a nice once since I have more OBDII vehicles now.

 

snap-on scanner...

they aren't cheap. If you have any friends that are a mechanic for a living, that is your best bet...there are other brands as well, but I know for sure snap-on ones can read live data from the ECM and PCM. that life data for the apps is what you need to see to properly diagnose it. if it is jumping around with numbers at idle then its faulty. if you hold the pedal steady and it jumps more than a couple numbers...faulty...

you get the idea...