Boost pressure related derate

[Dragonfoot]

2005 ISX 15, demandated. When boost pressure reaches 34 lb it will derate to 20 lb or less. Comes back slowly in about 20 seconds. Just started at mandate removal. Engine runs so much better at low RPM but have to be careful with the throttle on hills. Any help would be greatly appreciated! Thank you so much

[tree98]

I'll bet my right leg it's a bad demandate. Pull the program and send it to Rawze for review.

[Bengy88]

Something I’ve learned is if you have to unplug the egr valve then whoever made the file for your truck was lazy at best, and if you say something to them about it they say things like why would you go further and do more if you don’t have to. So my first question would be is your egr valve un plugged? My second question would be did you or they block off your egr cooler? If not your egr valve could be forcing open in higher boost conditions which would explain a loss of boost pressure. But either way your file does need to be checked especially if it just started after the demandate. If you have a pc and a diag connector I can help you pull the file. Just shoot me a pm with some contact info

[Rawze]

(01-16-2023 )Dragonfoot Wrote:  2005 ISX 15, demandated. When boost pressure reaches 34 lb it will derate to 20 lb or less. Comes back slowly in about 20 seconds. Just started at mandate removal. Engine runs so much better at low RPM but have to be careful with the throttle on hills. Any help would be greatly appreciated! Thank you so much

What you describe is the classic, well known symptoms of a bad delete. There is a set of turbo derate issues that do exactly what you describe located in the ecm memory that persists after some completely clueless person flashed your truck, and likely never addressed.
Here is some info on this at about a third into the post...
http://rawze.com/forums/showthread.php?t...4#pid64964