2006 ISX CM870 High Pyro, surging under load

[sickoftrucks]

2006 ISX CM870 High pyro reading, surging under load. it is a known truck to me, tri-axle dump. KW T800. It was brought to me with high pyro reading, and black smoke, low boost. 1100-1200F. we found the turbo unison ring stuck and broken in the turbo. Replaced the turbo, it runs great, has boost, but still high pyro, 1000-1100f. and it surges under load and boost fluctuates with the surge, it is cutting fuel back. turbo and egr test good in insite, took out the egr valve to inspect, it looks ok. it feels to me like it is overfueling, and the ecm is cutting the boost to protect the engine. also, no codes, we have insite pro. Help

[tree98]

Where did you get the turbo from?

[sickoftrucks]

Supplier i use all the time. It is a air actuated vgt, not electronic. If the problem is with the turbo, my guess would be it is the controller as opposed to the actuator. This is not a vgt with an electronic controller. Thanks

[Rawze]

Is your replacement turbo an OEM certified reman or origional? -- or repaired/re-manufactured by some shop?

CM870 air actuated turbos can be tricky to install properly sometimes. Some have a floating ring (can turn freely and self-align) in the exhaust housing for the vanes to move in and out of, and some have a fixed ring (fixed shroud plate). if the one you just got has a fixed ring in the exhaust housing then it will hang, jump and not operate smoothly if the turbo was not installed onto the truck exactly right.

I.E.>Fixed ring (non-floating shroud plate) turbos cannot just be installed onto the truck without some adjustments and testing.

The older style were fixed ring, and it is also well known by turbo shops that reman holset VG's that even with the floating ring style, as they age, the ring seizes up permanently and cannot be freed up again even after cleanig, etc. and a rebuild ... Turning it into a fixed ring style. - Does not hurt a thing as long as the installer is made aware of this fact so that the extra alignments can be made on the truck during the install.

Turbos with a fixed fixed ring require the person installing it to remove the actuator (the air actuator in your case) from the control arm after mounting the turbo to the exhaust manifold and feel the control arms in/out movement by hand. The v-band clamp needs to be loosened on the exhaust side of the turbo a slight bit so that someone can clock the main body of the turbo one direction and the other a bit (a very fine adjustment amount usually) while the vg vanes are fully extended into the exhaust ring and find the centre point where they do not rub. - It does not take much mis-alignment at all for the whole thing to operate wonky if the vanes are rubbing against the fixed ring as they go in and out. On these types of turbos someone needs to always do this after mounting it to the exhaust manifold on the truck. This is because it is very common for this alignment to be slightly out of adjustment once the turbo is put in place.



Moving the arm in and out and adjusting the center housing to the exhaust housing alignment for the smoothest, least resistance is quite important, especially on CM870 because the ecm has no feedback for the vg movement and it has no idea if it has actually moved to the correct position or not.

- I would start there. Once that has been done correctly, you can also check the movement of the turbo air actuator by making an adapter and supplying air from a regulator and see if the actuator movement is fairly smooth and consistent from 0 to ~30 psi (maybe 0 - 60 psi, i forget) both before it is installed onto the turbo and after.

Tags:

air operated turbo, cm870 turbo, turbo problems, turbo hanging, turbo wonky, turbo issues, cm870 boost problems

[sickoftrucks]

Took the actuator off, the lever moves perfectly smoothly in both directions. So i did not loosen the exhaust side clamp to change clocking. The actuator is new, and is operating smoothly. I am going to run the injector test again. After i ran the test last time, the truck did not want to start, like it was out of fuel.

[sickoftrucks]

We ran the injector test again with insite. It passes. We did find a blown 10 amp fuse for the lift pump. The pump now works, but nothing changed. We also found the fuel is black, can't see through it, but no oil consumption that we know of. I just drove the truck again. It runs well until you give it throttle over 1500 rpm. then it surges, meaning power is not steady. Pyro goes up fast to 900-1000f. it is pretty gutless as well. No smoke except a small amount when you shift and step on it. last item, there seems to be no 3rd stage engine brake.

[Rawze]

Anyone bother to put regulated air on the turbo actuator and slowly raise/lower the pressure to see if it is hanging up, jumping, or acting funny?.

Has anyone replaced the turbo controller?


What your now describing could also point towards bad delete programming too.

Did someone put a delete program in the ecm?-- If so, by who?

[sickoftrucks]

There is no delete programming, the truck to my knowledge is 100% stock. Basically, the two problems are the high pyrometer temperatures and the surging. As i mentioned before, the fuel is black as can be, i am having it tested now. I suspect the injectors are causing over fueling, and the over fueling is causing the ECM to cut back the fuel due to high exhaust temp readings. we need to run the test where the engine runs on one cylinder at a time before anything else. Turbo controller has not been changed. i watched some of your videos on testing the injectors. I need to see what we get for results before moving on. Thanks

[hhow55]

(06-16-2020 )sickoftrucks Wrote:  There is no delete programming, the truck to my knowledge is 100% stock. Basically, the two problems are the high pyrometer temperatures and the surging. As i mentioned before, the fuel is black as can be, i am having it tested now. I suspect the injectors are causing over fueling, and the over fueling is causing the ECM to cut back the fuel due to high exhaust temp readings. we need to run the test where the engine runs on one cylinder at a time before anything else. Turbo controller has not been changed. i watched some of your videos on testing the injectors. I need to see what we get for results before moving on. Thanks

the fuel is black as can be.

Your tanks are infected with algae, which could cause surging