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+--- Thread: Isx cm870 boost in and out (/showthread.php?tid=6976)
Isx cm870 boost in and out - wellrun - 01-28-2021
I've got a 9400i with a 450 cm870 isx I recently purchased..... problem is that I can hear the vgt intermittently goes in and out when ever I'm driving loaded at times it cuts out and I loose power then it suddenly comes back in...... I have a manifold leak at number5 cylinder.... could that be the problem)??? Truck has been demanated
RE: Isx cm870 boost in and out - Rawze - 01-28-2021
Have the programming checked right away. E-mail a copy of it to me for inspection.
It is a CM870 though, and that air operated turbo controller is notorious for acting up or being a bit wonky as well. Could be mechanical issues, could be programming.
Maybe hook up an air supply to the actuator ans see it it operates smoothly from 0 to 60 psi slowly thru its range of operation and does not hang up on you. After that, maybe test the air controller for it and also check to ensure your getting proper air pressure to the turbo circuit controller.
Next would be to pressurize the whole engine up to 30 psi with some block plates and regulated shop air and fix any leaky circuits.
RE: Isx cm870 boost in and out - tsolson - 01-28-2021
mine was the turbo air controller. but check it for leaks, and make sure there are no leaks in the air line running from the turbo controller to the air actuator on the turbo. Mine is a low mount, on the LH side of the motor, behind the frame rail, at the front of the engine. They changed some to a high mount, not sure what you have.
with mine, if I shut the engine off, and restarted it, then it would boost normally for a while, then it would quit again. I replaced the controller, and it fixed the problem. last one I bought was $1100 CAD, and I'm sure they haven't gotten any cheaper. Cummins did replace one on parts warranty for me, but i think those days are over now too, unless they diagnose it for you in their shop.
RE: Isx cm870 boost in and out - marek4792 - 01-28-2021
(01-28-2021 )tsolson Wrote: Mine is a low mount, on the LH side of the motor, behind the frame rail, at the front of the engine. They changed some to a high mount, not sure what you have.the high mount actuators are the earlier models and more robust imo, the low mounted is the newer style.
RE: Isx cm870 boost in and out - Chamberpains - 01-29-2021
Absolutely check that low mount VGT controller. Does this problem happen with the high Jake brakes also? Intermittently not boosting high enough?
The simplest easiest way to check controller function is If you have access to a known good VGT controller off another unit. Swap yours for it for a week and see if the problems go away. Other than that its basically process of elimination. If everything else is good than the controller is one of the last and a bit pricey things to eliminate. If you do have to replace it, don't go to fleebay and some half ass reman site. Buy OEM Holset only. The rest are absolutely garbage. I went through 2 crap remans before going Holset genuine.