CM870 EGR Woes

[DadBunz]

I have a friend with a W900B that is an ISX truck. Original engine got pulled and a 03/06 CM870 was installed. He said that it hasn’t really had the power that it should since the swap and now it is only making max 20lbs boost and has EGR codes. 2791-7 was the active code and would come on every time the EGR would try its initial sweep in the first minute or two of running the engine. The light would go out as he would start driving until getting into a hard pull that would require boost. He complains of how lazy the throttle is like it is in a “safe” fuel map and maxes boost at 20psi. I pulled the EGR valve off per a Cummins tech thinking the valve is physically stuck. The valve is not physically stuck and is actually fairly clean. I put it back on and started checking wiring. 5v reference is steady, signal return has 0 resistance. I even checked the PWM with the multimeter and although not scientific, the meter cycled up and down so I believe the pwm is fine. Test drive and no change, light comes on and still only 20psi boost. Picked up a dorman EGR. Just as a test i plugged it in hanging off the side of the engine with the old egr still mounted to the exhaust. No codes, took it for a test drive still only 20psi boost. With the engine idling and warm the new egr valve hanging on the side sits there and cycles open and closed as i would imagine the ecm is commanding. Thought we had the check engine light figured out at least. Put the dorman egr on and barely made it out the shop door and check engine light came on. Took for test drive and was worse. Almost no boost, no power. I assume it went into derate this time. Checked the codes and it is showing 2791-5, 2791-7 and 27-5. So i hang the old EGR valve on the side and plug it in and it cycles once and throws the original 2791-7. I do not have Insite, only a basic Nexiq. The ECM is a used unit from a 2004 from the cummins shop. My question is, do i have stray voltage coming through the engine block causing these issues? Is it possibly a bad ECM? Bad new EGR that is shorted internally to ground? At this point I think the boost issue is unrelated because it struggles to make boost with the egr closed and no codes. Any insight*** would be appreciated or if anyone has ever chased ghosts like this before I need some pointers before we send it to sit at the cummins shop for weeks.. Trying to help a friend and it seems to be backfiring. Thanks

[Rawze]

== First of all, stop treating the engine/vehicle like its a junk yard rat rod. All you get is half-arssed garbage can results.

== PUT only OEM origional parts on it and get that garbage DORMAN TRASH!!!! sensors, valves,.. or anything else non-OE branded s$it off of it!.

== GET INSITE!!!! because without it, your pi$$ing in the wind!. Insite can be had form the engine maker,... or on the cheap off flea-bay or some shady wwwsites with permanent key for hundred bucks or so. No excuse not to have it.

== USED ECM = U*SED ECM PROGRAMMING that does not belong in the engine... even if program is same name. == RE=FLASH THE ECM with fresh OEM software, even if its the same version, etc.. as it will wipe out all old settings, balancing, etc.. and make it re-learn the engine.

== FIX ITS ISSUES that it is complaining about and stop half#assring it with cheap-o garbage can ideas and solutions. - ITS A $40,000 COMMERCIAL ENGINE!. TREAT IS A SUCH!.

== DO ALL maintenance on it .. assume no one has ever done it before. Injector leak tests, valve adjustments, crank shaft damper replacement, clean out the oil screen behind front cover so no CC fumes pressure can build up,.. rod/main bearing inspection, ALL new sensors for intake, egr + Delta-p block cleaned out, and exhaust sensors + its Exhaust pressure sensor passage cleaned, , etc.etc.etc.etc. -- ONLY OEM SENSORS as those after-garbage sensors never read quite right and make false mis-fire alarms, etc!.

== Pull arm off turbo, make sure movement of arm is smooth and easy to move. - Replace controller if its many years old + make sure the supply air line going to it regulated at 92PSI that feeds it. Some of the older 870's, this line was not regulated (or had inline filter that would clog up) and made turbo wonky.

== you can UNPLUG THE ERG TEMP SENSOR to put engine into its no-egr operating mode properly .. NOT the EGR valve, when troubleshooting the EGR syustem. This closes the egr completely and runs engine without it safely, as long as no idiot screwed with the ecu programming.

== Monitor the engine state, etc. in insite,.. see what the ecm is complaining about when power or boost is being held back!.

== With EGR valve unplugged, turbo will make 36-psi for a bit, then fall back to 32-psi or so as a protection of the egr disconnected.. but THIS IS NOT A POWER DERATE, only a boost cut-back ... full power/torque will still happen. - Get it running well on the 100% factory programming with the numbers I post here before even considering taking it any further.


== Disconnect exhaust piping right behind turbo on test drive. If boost increases at all, then there is exhaust issues!. clogged muffler, .. something wrong.

== After-garbage CAC units are also horrible!.. restrictive too,.. so this can be issue too!.

== I.E.> ALL OEM ... ALL THE TIME!... nothing less.. or you get less of a result!.

==================

Lastly.. THAT MODEL ISX DOES NOT HAVE THE SAME LOW-END RESPONSE AS NEWER MODELS!. It is softer on the up-take overall.. AND THIS IS A GOOD THING!... as it made them last longer than newer model ISX's that typically get tortured to death on the bottom end of their operating range. ISX's hate low-end torque. its called lugging them,.. and it cuts engine life in half or less if you run them at thigh torque and pedal positions below 1500 rpm that way.

[DadBunz]

I tried to get him to not buy this truck because he likes Caterpillars and that’s how he tries to drive it. I’m not a diesel mechanic and don’t want to be. The place where everyone here in eastern iowa takes their Cummins engines said to not put an oem egr valve on it because they are junk… The shop that put the engine in the truck didn’t even put new air filters in it. It does have a newish CAC, didn’t look to see if it is aftermarket. I will report back to the owner and see what he wants to do. Thanks