CM2350 Turbo Spooling at Idle

[rgunn111]

I've had this issue for about a year, and I've seen mention of it on multiple Facebook conversations but have yet to come up with a solution. My truck often sounds like it's trying to regen at idle or low RPM (under 1000). It's sporadic, but happens several times a day. The engine does not idle up but the turbo does. If I'm stopped and I use the cruise control to set the idle it stops. Turn the cruise off and it starts again. If I let the truck just sit at idle at the end of the day it will stop doing this after about 45 minutes to an hour. The regen (hot exhaust) light does not come on and it is not logging a regen in insite. Instant fuel consumption on the gauge cluster jumps to about 1.6, 1.7mpg. Compared to less than 1mpg at normal idle and over 5mpg during a forced regen.

Does anybody know what might be causing this? I recently read about a possible leaky 7th injector but haven't been able to find the thread again.

Thanks in advance... I've been lurking for over a year.

[RollinCoal]

Demandated ?
If so pull a copy and mail it to Rawze

If not you will need insite and watch your exhuast temps to make sure there getting where they should be

[rgunn111]

(08-12-2022 )RollinCoal Wrote:  Demandated ?
If so pull a copy and mail it to Rawze

Negative. Just had the DOC and DPF cleaned at my local Peterbilt dealership. It was doing the same thing, before and after.

(08-12-2022 )RollinCoal Wrote:  If not you will need insite and watch your exhuast temps to make sure there getting where they should be

I have insite. Temps look good I think. I have the regen history on my truck PC. I'll see if I can post a screen shot.

[Rawze]

(08-12-2022 )rgunn111 Wrote:  

(08-12-2022 )RollinCoal Wrote:  Demandated ?
If so pull a copy and mail it to Rawze

Negative. Just had the DOC and DPF cleaned at my local Peterbilt dealership. It was doing the same thing, before and after.

(08-12-2022 )RollinCoal Wrote:  If not you will need insite and watch your exhuast temps to make sure there getting where they should be

I have insite. Temps look good I think. I have the regen history on my truck PC. I'll see if I can post a screen shot.

If you look at facefook and other places, I am sure you will get a lot of garbage answers for a question like that. This is because ppl do not know know how the engine or its ecm actually works.

What the engine is doing is regulating the exhaust can temperatures. If that DPF, DOC, SCR cans are not at operating temperature, close to 500-Deg F, then the engine will not pass emissions. It is required that the engine maintain those operating temperatures on the exhaust components. The exhaust cans cannot function properly if they are too cold or too hot by any large degree.

The engine makes extra heat for them by changing operating modes, choking the exhaust manifold with the turbo + creating excess friction in the cylinders of the engine to generate heat to warm up- the cans. Once they are at temperature, the turbo relaxes, engine mode changes to some other mode depending on the situation, etc. until it needs it again.

There are more than 14+ engine operating modes in the CM2250, and more than 15+ operating modes in the newer engines. Operating modes with labels such as Alpha0, Alpha1, Chi2, Chi3, Chi4, Chi5, Chi6, Chi7, Chi8, Chi9, Chi10, Chi11, Chi12, (and on the newer engines, Chi13).
referenced in this document in detail: http://rawze.com/forums/showthread.php?t...5#pid67395

[rgunn111]

Does this info help at all? I read the entire MM document... I'll probably have to read it a few more times for everything to soak in. I have Insite and am about to start looking into CT.

This is my latest regen history. Lines 1-3 were driving home from my most recent trip (approximately 500 miles). Line 4 was a parked/forced regen that I ran at the truck stop after clearing a CEL for "regen too frequent." Lines 5-8 were regens that occurred driving from my house to the truck stop (again, approximately 500 miles). Line 9 is a successful regen after reinstalling the "cleaned" DOC and DPF (I removed and reinstalled, took them to my local Peterbilt dealership for cleaning).... Line 9 here is Line 1 of the next attachment so... skip down.



Line 1 is a passed regen after reinstalling the DOC/DPF. Line 2 and 3 were failed regens. I ran the "regen analyzer" instead of the basic regen program. Both times failed with an error "Turbocharger speed is above the maximum specification." Lines 4+ were prior to having the DOC and DPF cleaned.



And just for reference, here are the DOC/DPF prior to cleaning. Note that when I took everything apart I cleaned the differential pressure tubes with carb cleaner and cleaned the thermocouples with steel wool.

DOC outlet

   

DPF face

   

DPF outlet

   

[Rawze]

the "Max DPF Pressure" in Inhg on the far right of those screen shots should average below 3.0 for a healthy system.