Cm870 low boost high egt

[Oilysnowman]

(01-28-2026 )Rawze Wrote:  

(01-28-2026 )Oilysnowman Wrote:  

(01-28-2026 )Rawze Wrote:  what are you calling high EGT's?.

1000 Fahrenheit post turbo. Occasionally it shoots up fast to 1100 when I shift and that’s when it gets the pressure differential derate actually, then the the boost shoots up to 40 or just over and cools it down then the boost slowly drops back to 33 ish. It was some other derate just for egr that came on with the engine brake. Sorry got my wires crossed there.

That EGT is not excessive, but the boost going above 37~ish is.

1050 - 1100 F (post turbo) is the upper end of acceptability for the ISX under max operating loads.

what you describe almost sounds more like the arm is hanging up?.. is wonky?. etc. - that could be the turbo itself.
related info: https://rawze.com/forums/showthread.php?...8#pid54418

So I have ruled out that it is the turbo itself, I also swapped the turbo control module with one I changed out a year or two ago that was working, but leaking air. Didn’t make any difference so I put the new one back on. That doesn’t rule out the module completely, but I would think it would act at least a little different. Long story short, high air density, low boost. Low air density, boost is pretty good. I understand it takes its air density readings from ambient pressure, and intake air temp? I have new sensors there. Ordered a new intake pressure sensor, it’ll be a week before it gets here, exhaust pressure sensor is under a month old. Google said it could be the coolant temp sensor, does that make any sense? I’m running out of ideas.