Cummins ISX 870 turbo boost issue

[Rawze]

Don't fight ghosts ...
(possibility of bad delete file)...
Its a CM870... They don't shut down like newer trucks when egr system has been unplugged ...

If it has de-mandate programming in it then put the factory software back in it. This will eliminate any programming problems while you troubleshoot the rst of the engine issues.

If it is factory programming, make sure the program in the ecm exactly matches the enigine ser# according to quickserv.com

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After factory programming in back in it,.. the EGR temperature sensor (hidden somewhere near the fuel filter on drivers side) can be unplugged to shut down the EGR system for troubleshooting, etc. CEL wil be lit but engine will not shut off for this. Matter of fact, some people just drive them like this and never look back..lol

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How much boost is it making when you say it spikes?.

How much boost does it drop back to when is falls off?.

What is engine ser#?. what make/model truck?. Mileage, etc?.

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(if it is non-damandated )...

Has the EGR delta-P sensor and mounting block/passages been replaced/cleaned out?.

Has the EGR valve been checked to see if it is hanging up?

How old are all the sensors? - replace ALL on the engine hat are more than 5+ years old (with oem only) ... regardless of condition so that the ecm is not getting off-putting data.

Are the sensors all OEM?.. if not then replace them to OEM immediately, as non-OE sensors are notorious for making engine act up.

Has anyone bothered to remove the control arm from the turbo and move the VGT by hand to ensure it is smooth and not scratchy and hanging up, etc?. - Both at rest,.. and again while engine is idling?. - if that thing is not butter smooth in its movement, it will surge and act up, then do wonky things.

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Lastly, it should be noted that if the EGR is disabled in any way,.. unplugging the egr temp sensor or egr valve, or delete programming that was not done properly, .. then the engine will have normal boost (36-38 psi) on every hill it sees for a brief moment,.. then the boost will drop back to about 32-psi and then hold at the lower pressure.

- This is a well known boost derate (but does not reduce power) due to the auxillary emissions systems not being switched off properly during improperly done delete programming. Make sure your not fighting this ghost issue, and then thinking that something is wrong with the turbo or controller.