2006 ISX CM870 High Pyro, surging under load

[tree98]

The ecm doesn't know your getting high egt's, there is no sensor for it. The black fuel is probably asphaltane, pretty common occurrence. As Rawze mentioned, did you put regulated air to the turbo actuator to verify smooth and full range operation? Also could be the turbo controller as Rawze mentioned. Replace it with a genuine cummins NOT an aftermarket of any kind. These controllers can give you problems and never throw a code

[Rawze]

If the fuel is black, testing it via a lab is the proper way to find out what the contaminant is.

Algae can be treated. Ashpaltine can be kept at bay with better fuel filtration such as a 7 or 10 micron filter in the fuel water separator unit (davco or other). I prefer and run a davco with a 7-mocron filter in it ... the davco particularly because a person can see if the fuel is getting aerated on the uptake due to fuel lines getting leaky or other things like cracked pick-up tubes in the tank(s), etc.

You mentioned high pryo readings...
Do you have an aftermarket pyro on it? - or are you only relying on the ecm's calculated reading?.

Never trust the ecm's pyro data on the ISX ...

The ecm does not use an actual pyro feedback sensor for its readings. It is a calculated value based purely on estimations. It is usually fairly accurate under steady engine states, but it is well known to show some crazy or unusual high spikes/readings at brief times when shifting gears or any other time where fuel supply to the cylinders suddenly changes.

I.E.> any ISX that is having surge issues, the ecm may very well show some higher than normal if not ridiculous at times EGT values vs. an actual gauge with sensor that has been placed in the exhaust. -- Never rely solely on the ecm's pryo readings, all the ISX engine have this issue with the calculated pyro given to insite and other software that the ecm provides.

You have not specified that i can see, where you say the high readings are coming from. Does it have an actual after-market pyro gauge installed into the dash? -- If so, is the sensor for it Pre-turbo? or Post turbo? -- Or are you relying on only the ecm feedback.

In any event, unusual pyro readings are the result of other things ... and will not be the causation of any of the surging like your describing. - It is the other way around, where the unusual surges, other isues are causing the pryo readings to go crazy (ghost, real or otherwise). - Monitoring the 'Fueling_Control_State' live with CT software will reveal what system is actually in control of the fuel supply requests at any given moment.

Has anyone bothered to unplug the egr temp sensor and tested the truck/engine? -- to see what happens with all the emissions shut down and the engine locked into only one operating mode? -- That would also be something that could help to eliminate if the engine is choosing the wrong operating mode(s) or if the problem is suspect to be emissions related.

[JimT]

I seem to remember, in a thread a few months back, that someone mentioned a possible cause of surging to be unburnt hydrocarbons being reintroduced to the air intake via the EGR. Not sure if that was a true cause or what, but I had the start of some minor (and random) surging just prior to disabling the EGR on my truck.

Anyway, just a thought to throw out there.

[Rawze]

(05-31-2022 )Sage91 Wrote:  ...
How do you tell if you have an old style fixed ring, or new floating style? I am installing new turbo on my truck, engine is an 06 cm870

by removing the air actuator from it and checking the movement of the arm to ensure it is smooth and that there are no spots where it wants to hang up.

[Kbarnes0]

I'm going to join in on this one as it states almost identical to what I was going to post. 06 CM870 high pyro above 1500rpm. I don't have a surge. This load gross weight final put in enough load for me identify that it pulls really well at 1450-1500rpm and maintains steady egts. As soon as you drop a gear if it's over 1500 you really got to back out and feather it.
Mine is demandated with a tune from a group member. Aftermarket boost/ Egt gauge. prob is pre turbo. Boost range is smooth and peak I've seen is 35/36. Typically 1700rpm/1200pyro would be 25-27psi. Not sure if it should be able to operate towards max boost pulling hills, but you can't get anywhere up there, so I just back out of it and go slow.
I was thinking high pressure pump not keeping it fed?
Hopefully we can identify the cause. I will work through a few of the previous mentioned items as well.
Does the cm870 have the command fuel pressure in insite? Or just rail

[Rawze]

Fuel pressure on a CM870 is totally mechanical. The ECM has no control over it.

Also, 1190-F is about right as far as top end EGT's go, pre-turbo (1050-F max post turbo) in a hard pull if you try hard enough.

What you don't want is for it to run abnormally cold due to pi$$ poor programming for whatever power it is making at 100% throttle ... that is the killer of the ISX.

Of course, most people do not tend to drive their engines that hard, so they tend to back out of it when it gets to about 1050-F (950-F post turbo) or so to help the longevity of the VG turbo.

[Nilao]

I back off mine @ 850 pre turbo Temps

[Kbarnes0]

Gotcha. I think I'm up against a mechanical issue. All diag tests insite pass. Each cyl running single sounds the same. Finishing this run it developed a cylinder imbalance code. I can tell it's definitely lugging on at least one.

Should I do the bubble test to see if there is a faulty injector that the insite test doesn't see?

[tree98]

That's where I would start