2013 ISX 15 CM2250 Low acceleration, power, and mpg.

Hey guys, recently purchased a used Peterbilt 579, with the engine mentioned above, and have been having major issues regarding power, acceleration, and mpg.

The truck feels as if it has almost no power. Be it pulling away from a stop, accelerating quickly, or pulling up a hill. It just feel overly weak with everyone around passing by with no problem. Hills are a serious challenge here.

We started diagnosis with filters, replaced both fuel filters, the air filter, urea filter, oil filter, and fresh oil, so everything is clean and brand new. The engine definitely sounded better after all that but it still just doesn't have any power when pulling a load.

Boost pressure regularly is maintaining at 28psi under heavy load (which from what I hear, is well within reason for this year engine), no fault codes are being shown, have looked into Cummins Insite and have found nothing troubling, everything passes tests. Have cleaned the IMAP sensor, which helped a little, have checked for boost and manifold leaks, and everything checks out okay. No smoke is exiting the exhaust and flow seems good. Random tidbit, the engine fan seems to kick on very frequently and without good reason. (In another thread here someone asked about it with similar issues to myself, but got no response.)

I am bewildered when it comes to what is happening. There seems to be no specific symptom other than the lack of power, and bad mpg (which is getting worse. Started around 6.8, down to 5.7 mpg pulling the same loads) I'm at a loss for ideas of what it could be. Short of taking it to Cummins and having them run it in the dyno (really trying to avoid due to the expense and downtime of doing such), I have no idea what to try next.

I've scoured the internet looking for anything that could help, Delta-P sensor, EGR valve, EGR tune-up, and while I'm in progress of trying each of those, I have my doubts they would cause such a major loss of power.

With all the diagnostics I have performed, and with even another technician checking Insite and giving the OKAY with no trouble codes. Is there anything you guys could think of that would help me here? The only idea I have is the ECM is limiting the fuel, some kind of clog in the exhaust system, or there possibly being something wrong with the fuel system, such as a fuel pump or injector.

Any help would be greatly appreciated as this thing is driving me insane!

2013 ISX 15 CM2250 547,000 miles
If it help, this used to be a fleet truck, and was governed, they removed all the governing, and that has been confirmed within Insite, but not sure if something they did would've caused such an issue like this)

 

For sure. I've already sent an email to try and get an invite code to join the forum. Seem like great folks over there!

 

I've questioned this myself, and have heard of a "silent derate" on occasion. Given there's no codes or diagnostic errors being thrown, how would I be able to diagnose and resolve the problem? Is there certain parameters within Insite I could check to see if it's being derated/reset. Also would the derate cause such a loss of MPG? Thanks!

 

I've read the thread on Rawze about incorrect CAL's being installed, and the symptoms being a silent derate. Is it possible the team that removed the governor from the previous company owner, reset parameters/installed the incorrect CAL for this engine? Would it hurt to download the latest from Cummins and flash it myself considering they release one every 6 months?

Now that is a good question, I'll have to make a manual measurement later today with some help, as neither of the rear axle plates are stamped with the actual Ratio. (Don't you just love when someone doesn't do their part?)