Derated C-15 Acert MXS Help Please...

Hello everyone,

I have got a MXS C-15 ACERT that is derating itself and not displaying any codes.

Basically what happens is when I build 43 psi of boost pressure I can hear the turbo "unspool" and I can only build 30 psi of boost until I stop the truck and shut down the engine and restart it, then the truck goes back to full power until I induce a load that requires 43 psi of boost again, then it derates again. There is no Check engine light nor are any codes logged.

I have had it to several CAT shops and even they are scratching their heads. When it is hooked up to ET there are no logged events and no logged codes, however, every time that the truck derates at exactly 43 psi of boost, there is a status flag that is displayed in ET that says "Intake Valve System Starting" but the cat dealers have no clue...

Has anyone else encountered this problem?

Any help or suggestions would be greatly appreciated!

 

They should be doing some VVA tests as well as cyl cutout tests.. by monitoring the contribution rate they should be able to figure out what is wrong... also you need to have a close look at the top end..valve set history and or loose broken rocker bolts are critical with this engine.While your in there remove the vva solenoids and look for any sticking plungers...with the engine running watch to make sure the vva plungers are not moving in the bore.. if they are bouncing they are holding the intake vlaves open indicating a mechanical problem.

vvas can stick open causeing a miss or derate, however usually if so much as hickup occurs it will log a fault. also if the vva oil control solenoid on the side of the base is sticking it wont releive the pressure in the oil gallerys posibly keeping them on but we should see "not responding faults"..

It is entirely posible there is an inrange sensor fault not logging faults..do you have aftermarket flash file ?? if not make sure you also have the latest and greatest flash file..

When the problem happens Toggle your set/ resume switch and it will trigger a snapshot. if you have a competant tech it should be fairly easy to figure out what is causing this issue...

 

Thank you KaptainKenworth and yes, they have been through all of those tests, have checked valve lash, rocker bolts, actuators, different flash files, etc. What it has come down to is that every time the engine builds 43 psi of boost the engine derates due to an "Active Status Flag" that comes on when the tech is hooked up to my truck with ET and he is riding along with me that says "Intake Valve System Starting" As soon as that status flag is displayed, it derates and will not uprate until I shut the truck down.

Has anyone heard of the "Intake Valve System Starting Active Status Flag"? If so, what makes it trigger and why?

Thank you in advance...

 

the vva activate only when under load and the eng has reached optimum temp and parameters.. its posible the ecm is starting to loose its mind.

I cant remember the sequence of datalogging of the vva so i would have to do some digging into the flag.. but if remember correctly i believe its normal.

 

Yes, thank you Kaptain... Dr. Diesel has been assisting us with this issue and is more familiar with the more technical aspects that have been tried in an effort to remedy this problem.

He can probably describe to you more correctly what is happening.

I appreciate the time that you have put into my problem already. Thank you.

 

Has anybody looked at the status of the coolant temperature sensor reading when this happens? I believe if the coolant temperature sensor is sending a low coolant temperature signal to the ECM, it could be causing the issue.

 

Did you ever figure out the problem. I have a cat c15 sdp doing the same exact thing and cant figure it out

 

Ok so first things first. The guy telling u about harnesses is still in the stone Stone age. A truck would throw a multitude of codes if u had an injector bad. A harness bad would throw a code too and if it didn't you would notice it before this hard pull.
What is happening is your acert ecm is derating on the hard pull. I'm willing.to bet ur shake is like the Jake's are on. If u listen really close at say 1500 rpm you'll hear what sounds like the Jake being engaged on a setting lower than the lowest. What's happening is ur ecm is telling the injetors on cylinders 1/3/6 or whatever order to limit fuel. Then it tells ur Jake valves to open very partially. This leads to a heavy stutter there is no way in hell this would happen without this being the case. An injector bad wouldn't activate the ####ing Jake. U get the shake because u have say cylinders 2/4/6 running at say 425 horsepower and cylinder 1/3/5 runnimg 225. Download a non cat tune and run. I guarantee if u back off throttle and gain speed it will fix. The c15 is a dirty motor and cat tried to clean it up with tuning and twins opposed to def. FYI my 6nz does the same. As for injector harnesses going bad. The ecm is throwing the wrong voltage. Reflash and install new if that doesn't fix new ecm time. . And that would cause a stutter more than what the main post is discribing. And an extreme mechanical issue.

 

Also adding a new code would fix cats code what happens is bad injectors even a little off will shake because even will not change cause they only know a 100% sound injector. Turn it up to 625 with non cat tune and be worry free till it does it 400000 miles later then it's injector time.

 

Pretty sure after 7 years he figured it out.....