Motor revs while sitting still until brake is applied. Why?!

[tracklesstrolley]

So my girlfriend and I just purchased a 2006 IC CE200 to convert into our first skoolie!...But when I start it just to let it idle or let it run to use the heat while working inside, the RPMs steadily crawl up until I hit the brake pedal. It drops back down to a normal idle, then a few minutes later, the RPM starts going up again until I hit the brake.

Is this normal? If not, what could be the issue?

[PNW_Steve]

I have a truck that does that when it's cold outside.

The first time I noticed it, I had started the truck to let it warm up. I went back in the house and after a few moments I heard the engine start to speed up. My first thought was that someone was trying to steal my truck.....

The computer runs the idle speed up until I tap the brake, Just like you described. Once it is warmed up it behaves "normal".

[Brad_SwiftFur]

Originally Posted by tracklesstrolley

So my girlfriend and I just purchased a 2006 IC CE200 to convert into our first skoolie!...But when I start it just to let it idle or let it run to use the heat while working inside, the RPMs steadily crawl up until I hit the brake pedal. It drops back down to a normal idle, then a few minutes later, the RPM starts going up again until I hit the brake.

Is this normal? If not, what could be the issue?

Sounds like a cold weather warm up to me. Also some engines are programmed to do this to keep the coolant temperatures at operating range.


What engine do you have?

[MortonKA]

One of the spare busses in our Schools Fleet does the same thing. It kind of freaked me out the first time I drove it, but I got used to it.

It does this in any weather.

Apparently it’s normal, as several years later it still does it.

[ermracing]

Ours does that too (2003 DT466E). I haven't waited to see how long it takes to go back to normal idle on it's own. I also tried flipping the High Idle switch but it doesn't do anything. Like the others said, this isn't a problem, just the way it works.

[EastCoastCB]

weird. My 03 doesnt do that.

[PNW_Steve]

Originally Posted by EastCoastCB

weird. My 03 doesnt do that.

I have an '04 Cummins 5.9 that does it and an '02 Cummins 8.3 that does not.

Maybe it was a "new" feature around '03-'04?

[smokescreen]

Mine does that if the cruise control is left on and its below freezing, otherwise not an issue. This is on a 2001 Dt 466E.

[Apud]

I've got a 2002 Ford e450 that's been doing it. I read one website that stated if you hit the brake and it stops it's Regen. It is common in newer pickups and designed to burn of excess soot from a lot of idling. It will also complete the Regen process when highway driving. I figured it was put on school buses earlier because of all the idling they do. I have been letting my bus idle for long periods when working on it - for heat and a lot of stop and go driving so I figured that was it.