| Cummins ISX 870 turbo boost issue |
| Yesterday, (Subject: Cummins ISX 870 turbo boost issue ) Post: #1 | |||
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| Cummins ISX 870 turbo boost issue Hello, I am having an issue with a Cummins ISX cm870. It had showed up to me with a new turbo,new intercooler and a bunch of new sensors installed. The main issue is that under high idle or when driving the turbo will spool up, seem to be working, and than drop on its face and exhaust before respooling up and repeating this turbo loop. It seems to be building to much exhaust pressure, because if I unplug the manifold pressure sensor it no longer acts this way at high idle, but i do not want to drive it this way. It was having a pulsing/loping idle as well, but after reflashing the ECM to the most current insite update, it no longer lopes at idle. The barometric was skewed reading 23.6, so i replaced this and it reads accurately now. I was leary of the turbo control actuator box acting up so I have checked with a guage the inlet air pressure and swapped the box with a sister truck. I checked the exhaust manifold sensor tube, and it is free of restrictions. I notice it gives an egr differential psi derate going on and off as well on the data on insite when throttling. Hoping to have a little help with this problem child, I feel I am missing something simple here. Thank You | |||
| Yesterday, (Subject: Cummins ISX 870 turbo boost issue ) Post: #2 | |||
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| RE: Cummins ISX 870 turbo boost issue 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 ----- 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 ---- 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?. ------ (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. ----------- 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. User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!. | |||
(Online)| Yesterday, (Subject: Cummins ISX 870 turbo boost issue ) Post: #3 | |||
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| RE: Cummins ISX 870 turbo boost issue It still has egr and cooler installed and I am sure I have the correct oem ecm flash on the computer. I know the turbo is mechanically free, smooth as butter with the air actuator off. I also had the luxury of a sister truck to use for a day. I swapped a good amount of sensors to see if anything helped; boost temp and pressure, exhaust manifold pressure and checked ports, turbo intake temp, egr differential sensor and ports checked. Swapped turbo control valves. Sister truck runs fin with all these parts. Tried running with egr temp sensor disconnected and still does the spool up and waste issue. If I hold it anywhere between 1000 rpm and up,even at an idle when it doesnt build much boost,it will do it. So its not building much pressure at idle but it just keeps going full spool to waste. And you can see the exhaust pressure goin high and that's when it kicks out. | |||
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