Engine/Transmission (1998.5 - 2002) High Idle

[BigPapa]

Did you see the bulletin I posted?

 

[garylmoore]

I am idling at 1400 in park right now.
Intake must be toasty because the truck has run for a half hour.
Coolant temperature at 190 degrees.
If I put it in drive, the truck tries to Lurch, but my foot's on the brake, and RPM goes to about 1010.
Applying the parking brake does nothing.
Speedometer shows zero I cannot tell you if the apps is actually at 0 or not.
I'm going to pull it into the garage and pull the cover on the apps to see if anything is funny looking.

 

[BigPapa]

I'd find someone with a scanner that can watch what's going on live. It's almost got to be a sensor, programming, or the ECM.

 

[garylmoore]

I have no one around here that actually knows diesels very well and that I trust. There's a guy in Janesville Wisconsin but I've just heard about him through rumor.
So I'll probably end up driving the trailer down and back, and get the job done.
Deal with it in Indiana.

 

[garylmoore]

Thanks to everyone for your help.

 

[Topzide]

Just a thought, there isn't anything vacuum related on the engine were it could be leaking to cause it to high idle? Only other thing could be broken wire or corrosion causing signals to not get to where they need to go. If it was parked for a bit, might vermin caused some damage somewhere? From the diagram that I posted, could be coolant sensor as what @BigPapa posted, that's a cause for high idle. Just on the fence and throwing ideas to check. @garylmoore, Good luck with the gremlins and be careful with the built in "cruise control" with the high idle.

 

[garylmoore]

Yeah, I have decided to look at that coolant sensor connection, my buddy also suggested mice. I was told the sensor was located on the rear of the head, drivers side I think, that was on a gen 1 truck though. Others were located on the thermostat housing next to the alternator (that may have been gas engines, the article did not specify gas or diesel). Some with 1 sensor some with 2. I will see if I can find the sensor. Thanks.

 

[garylmoore]

Concerning the vacuum, does that have anything to do with idle?
I changed the power steering pump last summer (it really helped low rpm back up turns), and you about have to take the vacuum pump out along with it (no fun at all).
It would be interesting to know if that has anything to do with fuel. I will try to give it the Ole Hairy Eyeball tomorrow, but it is a mass of hoses down there. There could be a hose completely disconnected and you could still miss it.

 

[garylmoore]

Built in cruise control I can handle that part, the truck runs fine AFTER it is in gear. The big "CLUNK" when you put it in gear is the scary part.

 

[BigPapa]

No, your vacuum has absolutely nothing to do with your engine.

 

[BigPapa]

 

[garylmoore]

No, your vacuum has absolutely nothing to do with your engine.

Thank you sir...

 

[Topzide]

@BigPapa, Thanks for the clarification on the vacuum. Was just throwing out possible ideas to check on.

 

[garylmoore]

I'm going out now to check on the coolant temperature switch. I will check resistance cold then warm it up and check it hot.

 

[BigPapa]

I'm trying to find test specs or a procedure. Striking out so far.....

 

[BigPapa]

 

[BigPapa]

These diagrams are from the Cummins Service Manual for a 2001 School Bus, but should be basically the same as your '01 Ram, at least as far as Sensor locations. Obviously, things like the Tensioner, Fan Pulley, Oil Pan, and Exhaust Manifold are different.

 

[garylmoore]

I'm trying to find test specs or a procedure. Striking out so far.....

I checked resistance on the sensor and it would show a reading then blink out, this continued even after removal.
I called Chrysler dealer parts department and they wanted $141 for the coolant temperature sensor.
I told the guy would have to pass on that, I called Advance Auto and it was 51 dollars.
I bought it, replaced it, the new sensor was running 14.6 resistance. This did not change the fast idle.

 

[garylmoore]

I happened to talk to the guy at the rental place about my rental trailer. He had a Snap-On scanner and ran my truck.

Here is what I heard during that conversation, not sure what to think about some of it.

His scan showed three codes that did not show up at all on the dash or the code reader my friend has.
One was for an IAT sensor fault and the other indicated that the wastegate was stuck closed. The third was supposedly a companion code. Sorry I missed the numbers, but the guy was talking quick because he had to get back to work.
When he first hooked up the scanner, he also told me that with the key on, and a fully warmed engine, that scanner showed the grid heater on, and the IAT was reading 146 degrees.
He said the scanner showed the high idle was being commanded on by the ECM.
He also said Boost pressure showed 15 lbs with the engine off? How is that possible.

Sounds more to me like the engine computer is toast.

I'm coming down to the wire here, If I can't figure things out soon, I am taking the truck to a mechanic suggested by the rental guy. My friend offered to store my toolbox for the time it takes to have the truck repaired.
I will drive back in UHaul #4 emptying the house, and get the truck and toolbox later.

What do you think about that conversation?
The guy openly admitted that the only thing he had ever worked on were GM and he knew nothing about Dodge trucks.

 

[BigPapa]

I think if it were me, I’d replace that IAT. I may have one and don’t mind looking, but I wouldn’t be able to get it to you through normal channels till next week.