Cm870 all stock surge

[Hambone]

I have a truck with cm870 all original set at 475.Truck started to surge under acceleration. It throws no codes however if you disconnect the egr it runs fine in a silent derate. Ran turbo egr test and all pass . Replaced fuel filters no change. Checked fins/actuator on tubo all good. Just put a new egr valve on it and same thing. Egr cooler not leaking....any other ideas?

[Rawze]

do an EGR tune-up.. replacing the Delta-P sensor (and clean out the crossover tubes for it) + replace any other sensors that are old on the intake side of the engine.

also be sure to replace the exhaust back-pressure sensor and clean out its circuit thru the thermostat housing too.

[Hambone]

(02-15-2022 )Rawze Wrote:  do an EGR tune-up.. replacing the Delta-P sensor (and clean out the crossover tubes for it) + replace any other sensors that are old on the intake side of the engine.

also be sure to replace the exhaust back-pressure sensor and clean out its circuit thru the thermostat housing too.

Will do. Thanks

[Luckyjayb]

Great advice as always. Needing to do mine as preventative maintenance as well.

[Rawze]

(02-16-2022 )Luckyjayb Wrote:  Great advice as always. Needing to do mine as preventative maintenance as well.

it is a good place to start... but those CM870 can also start surging like that when the (air operated) turbo controller starts going bad too. - It is cheaper however to do a tune-up and cover the basics before starting to replace more expensive things is all.

[Hambone]

I tore it apart yesterday and the one delta p line was plugged solid. Cleaned it all out and she's running like a champ. Appreciate the advice.