CM870 Turbo Underspeed and Overspeed

[Rawze]

(10-05-2023 )pwhittle Wrote:  Serial number is 79079781. 2004/11 manufacture date in a 2005 vehicle.

Engine has 120k miles on it. Overhead done by Mr Haggs in 2017 at 80k miles.

Exhaust manifold recently resurfaced as a bolt had broken. EGR cleaned out at the same time.

The turbo underspeed code in stop/ go traffic is new after the exhaust manifold repair. The turbo overspeed derate was present before and after.

Paul

Did anyone bother to replace the EGR Delta=-P sensor and clean out its pipes, etc?.

Did anyone change the program in it to another program (to change the horsepower, etc)?.

How old is the turbo?

... and did anyone re-clock the exhaust housing and ensure the turbo was not sticky after the manifold replacement?.
here is some related info on this: http://rawze.com/forums/showthread.php?t...8#pid54418

Anyone replace the turbo speed sensor and check wiring for it to ensure they are good?.

Anyone test the turbo to see if the actuator is hanging up.. or is not smooth while the actuator is off of it?.

Anyone check/test the air operation and air controller for the turbo actuator?.


and last but no least at all.. How old is that muffler on that truck>?.. because those mufflers clog up on those trucks, or get restrictive after several years, and cause turbo issues too.


Like I said.. it can be a lot of things on those CM870's because they had that air operated VG turbo controller on them with n feedback to the ecm for positioning.