Archived Won't idle down

[retirednak]

Buddy called last night asking for help. He was on the way back from Moose hunting,stopped along the road to wiz,and his truck is idling at 1350 rpms. He shut it off,restarted and the same thing,won't idle down. I drive the 100 or so miles and we start checking for loose boost lines,fuel lines,anything out of the ordinary. No check engine light,no smoke or starting issues. Truck was running fine. I pulled him and his hunting buggy back to his house because he didn't want to risk breaking his transmission. We disconnected the batteries for an hour,hooked back up and the same thing. I hooked up my scanner to look for a possible hidden code and nothing.



Where do we start? His truck is an early '03 3500 SRW 4x4 with the 250 hp and auto transmission with about 66K miles. Its stock down to the air box.



My transmission was tired and hurt before I pulled him and his 9K trailer load. I hope it lasts till after tax time!

 

[Sticks]

I'd start with the simple things first. Look to see if there is anything (mud) keeping the throttle pedal from returning all the way.

Beyond that, you almost need a DRB III to see what the requested RPMs and actual are. If the ECM sees normal RPMs then it may be a crank or cam position sensor (you'd think that would throw a code).

Watching with interest, as my '02 has flaky moments where it maintains +200 rpms for a few seconds after I let off the throttle.

 

[retirednak]

We crawled all over the motor yesterday looking for loose connections,frayed wires,anything out of the ordinary. This guy keeps his rig show room floor clean and I would almost feel comfortable eating off the motor. I don't think this guy has driven off road more then once or twice.



We didn't find anything wrong visually. Last night he got out his multimeter and said everything was within spec. He did say that his tachometer was reading around 200 rpm's off compared to what his meter was reading. Not sure how he did that.



Since I also have an early '03,can anyone suggest parts that we could try off of my rig? He needs to go back to work Sunday and needs his truck. He refuses to take his rig to the dealerships in Anchorage and the one in Fairbanks,I wouldn't let them work on my lawn mower. So if we can swap parts and locate what is wrong with his,he can buy what he needs.



Thanks for the help.

 

[Sticks]

Start calling other dealerships across the country if you can not find anything here. Someone somewhere has dealt with this. May even try Cummins.

 

[tp0d]

Theres an APPS on the newer trucks, correct? Theyre drive by wire, no direct linkage from pedal to throttle. Possible his pedal position sensor is on the way out, might have got some water in it from cleaning the engine, or worse, some cleaning agent.

Try disconnecting the batteries for a 30min, then reconnect. Turn the key on, but dont start. s-l-o-w-l-y push the accelerator from 0 to WOT 3 times. Turn off truck, then restart as normal.

you could try swapping the APPS from your truck to his. as long as theyre the same thing.

good luck

-j

 

[retirednak]

He called the local Cummins dealer and asked and they have never heard of this. For grins he called one of the Dodge dealers and talked with the service manager. He was told it was impossible for the truck to idle that high or not to idle down. Said something about it being a safety issue (no *****) and engine management won't allow it. So he asked,why is it doing it then. Was told the throttle cable must be kinked or have a burr in it. My buddy laughed and hung up.



We'll swap APPS and see what happens,Keep the ideas coming.

 

[Sticks]

Didn't think the common rails had the apps issue we 2nd genners did.

 

[tp0d]

Its just a big potentiometer. Contacts wear out after so many cycles.

-j

 

[Sticks]

He called the local Cummins dealer and asked and they have never heard of this. For grins he called one of the Dodge dealers and talked with the service manager. He was told it was impossible for the truck to idle that high or not to idle down. Said something about it being a safety issue (no *****) and engine management won't allow it. So he asked,why is it doing it then. Was told the throttle cable must be kinked or have a burr in it. My buddy laughed and hung up.



We'll swap APPS and see what happens,Keep the ideas coming.

In retrospect, the service manager may be right. Is the APPS located in the engine compartment like the 2nd gens or did they move it to the cab on the pedal bracket? If it is in the engine compartment, then yes, the throttle cable could be the culprit. Still drive by wire, just the control for the wire happens to be the same cable used for manual throttle.

 

[Missouri Mule]

How about the FCA (fuel control actuator) I know when it starts to go it causes hard stating and rough idle but it mite increase fuel to the rail too.



I would look at anything that woud cause the ECM tell the FCA to increase fuel to the rail.

 

[retirednak]

My buddy went out to work on his truck again,he decided not to do anything with it over the weekend,it started up and is idling and running normal. WTF over? Now he has the noids about driving it any distance for fear that it will act up again. I told him you can't fix what's not broke. One thing he did notice was the charging system seemed like it was charging on the high side like if you've run the batteries down. He has to make a road trip to Talkeetna,so we'll see if it acts up again.



Thank you for all the ideas and imput.

Casey