Community Forums

powerboatr · 03-21-2019, 09:42 AM

Yes the rig had to be sitting at home for 12 months due to health.
So this past weekend we did our first shakedown trip and cleared the cobwebs.
so as we are hooking up the towed, the rv was idling as normal to finish warming up a bit.
as i was hooking up the engine idle started climbing up, not fast,,,just a slow roll up . So i went in and checked to ensure the fast idle was not set by the cruise control.
tapped the brake pedal and the engine went back to 699 to 720 rpm. so i waited and then it started the slow roll up, first to 799 and held, then it slow rolled up to 850, fluctuating to 890. then it did it again and rolled up to 920 ish, bouncing between 920 to 940.
i tapped the brake and it it fell to idle.
this repeated three more times.
so i shut her off and waited a few.
started it back up and within a few minutes it started doing it again.
so we started the trip and drove about 20 miles to get fuel. then another 60 to the park campground.
at the park..idled as normal, no fluctuation or jumps.
so i assume a temp sensor or something was seeing an out of spec input.
i never got any check engine lights or fault codes in the light bar.
any ideas.

FL420 · 03-21-2019, 10:23 AM

My ISC330 has recently started doing something similar. When I start it and let it air up the coach I do it at the normal slow idle. After a few minutes the RPMs slowly but steadily increase up to the 1200 rpm fast idle just as if I had used the cruise control switches but at a slower rate. I can slow it down to the normal idle using the cruise control switches.
Unfortunately I don't remember if the CC switch was on. I think I'll go check it out after the DW wakes up. She prefers me to bring her morning coffee instead of starting the Cummins.[emoji42]

powerboatr · 03-21-2019, 12:04 PM

it has only done this once since 2009

first time it was cold wet and nasty out and i chocked it up as it was trying to warm up fast.

i figured it was a ghost from sitting so long

onechaddude · 03-21-2019, 02:21 PM

Mine isn't an ISC but rather and ISB 5.9 of 2007 vintage in my motorhome. It does this as well and is considered normal. Many of the ISB engines in my Ram trucks over the years did the same.

I think what you're experiencing is normal, especially if its cool to cold outside.

Chad

Rollin101 · 03-21-2019, 02:36 PM

It is normal and does that if the battery charge is low.

powerboatr · 03-21-2019, 02:44 PM

Quote:

Originally Posted by Rollin101

It is normal and does that if the battery charge is low.

my batteries were fully charged,

one of the things i looked at was voltage and it was rock steady at 13.8 ..indicating the intake grid heater was off and not cycling.
by the time i got ol girl out of the port garage she was warm.
it was just one of them things that makes you go look and see
i think

other than a auto leveller freaking out at the cg..it was a nothing got broken trip

nothing like watching all the wheels come off the ground

Rollin101 · 03-21-2019, 02:53 PM

Quote:

Originally Posted by powerboatr

my batteries were fully charged,

one of the things i looked at was voltage and it was rock steady at 13.8 ..indicating the intake grid heater was off and not cycling.
by the time i got ol girl out of the port garage she was warm.
it was just one of them things that makes you go look and see
i think

other than a auto leveller freaking out at the cg..it was a nothing got broken trip

nothing like watching all the wheels come off the ground

The 13.8 was probably your alternator output not actual battery voltage.

powerboatr · 03-21-2019, 03:23 PM

Quote:

Originally Posted by Rollin101

The 13.8 was probably your alternator output not actual battery voltage.

yes, it mentioned it as it gave me indication the grid heater was not cycling, and that meant the engine was warm enough to not run up the idle to warm up.
just one of them things, that bugged me.

thomasd923 · 03-21-2019, 03:26 PM

2008 8.3 ISC. Mine does the same thing, will idle up to 1500 rpms, if I tap the throttle comes right back down. Probably some engine temp strategy.

oscarvan · 03-21-2019, 07:05 PM

Quote:

Originally Posted by Rollin101

The 13.8 was probably your alternator output not actual battery voltage.

By definition.....

DeetsMaggie · 03-21-2019, 08:27 PM

You guys didn't all indicate what model year, and thereby your SCR configuration, so this information may not apply. But on a 2018 ISL this "idle up" behavior to 1000 -1200 RPM is normal and directly related to the pollution/particulate control system. I cannot repeat accurately the details as explained to me by a Cummins mechanic, but basically the SCR system depending on several factors and sensor readings will call (via the ECM) for engine "idle up" to generate heat needed by the SCR system to either allow it to operate properly and/or prevent the system from being damaged or clogged.

This "idle up" generally happens on colder days after engine start up when SCR is otherwise not warm enough to operate as designed. On hot days or at highway speeds or when engine and SCR system is warm at idle after highway driving, the SCR system has all the heat it needs.

Understand that I have just told you more than I actually know.

Hope this helps,

DeetsMaggie

**Spdracr39** · 03-22-2019, 06:54 AM

Quote:

Originally Posted by DeetsMaggie

You guys didn't all indicate what model year, and thereby your SCR configuration, so this information may not apply. But on a 2018 ISL this "idle up" behavior to 1000 -1200 RPM is normal and directly related to the pollution/particulate control system. I cannot repeat accurately the details as explained to me by a Cummins mechanic, but basically the SCR system depending on several factors and sensor readings will call (via the ECM) for engine "idle up" to generate heat needed by the SCR system to either allow it to operate properly and/or prevent the system from being damaged or clogged.

This "idle up" generally happens on colder days after engine start up when SCR is otherwise not warm enough to operate as designed. On hot days or at highway speeds or when engine and SCR system is warm at idle after highway driving, the SCR system has all the heat it needs.

Understand that I have just told you more than I actually know.

Hope this helps,

DeetsMaggie

I think you probably nailed it.

FL420 · 03-22-2019, 08:59 AM

Quote:

Originally Posted by spdracr39

I think you probably nailed it.

Maybe if the coach has SCR, DEF and DPF. The OP's coach, and my coach, have none of that. In my case that was a major purchasing decision.

powerboatr · 03-22-2019, 03:33 PM

well thats easy, bus in in my signature but,

its a 2008 ISC, with only the DPF after treatment.

a note that on weds morning getting ready to leave cg, it was 45F and starting to warm up, with low humidity.
engine started normally and idled for at least 10 minutes while jacks were brought up and we hooked up the edge.
engine idled 100% normal. no idle up or mis steps, just steady idle.
on the day we left home and this even happened it was about 50F and with low humidity.

so if ecm was looking to warm up the DPF , i would think it would do it on both start ups.

i only brought it up as it was OUT of normal operation for my ISC over the last ten years. never thought it would become a russia incident.

and i am 100% sure the engine batteries were at least 95% charge state as the rv is 100% hooked up to power and the bird works perfectly, and the intial startup after sitting since sept, when it ran at high idle for an extended period during the a/c recharge. it fired up almost as soon as it spun over.