ISX surging

Lower HP. The derate gimps the motor via the ECM intentionally, according to Cummins.

 

Look, there are many stories about some "derating", I don't know all about it but remember one thing - there is even more stories about how there is slight increase in power despite slightly (like 2-4 PSI) lower boost. Bad, sticking EGR Valve can derate you too, so if you didn't look into it lately - take it off the motor and open it, easy job. Then there is also Exhaust Gas Pressure Sensor (one the thermostat housing) that can reportedly do crazy idle and lots of other problems. How many miles on the motor and all those emission devices? What year?

 

Already replaced the Exhaust Gas Pressure Sensor. When I said we're running out of thing to replace, I wasn't kidding. I'm in this one over $30k and climbing. It's a CM870 with a ton of new / reman parts. It has been to Rocky Mt. Cummins, Northwest Cummins, and a couple Fleet Prides several times.

Everyone threw parts at it to no avail, including a full rebuild with a new cam.

It's got about 12k on the rebuild now. The EGR valve has about 200k miles on it.

 

They throwing parts because they like to make good money but another reason is... they don't really know what to do, there so many variables on ISX and every other truck with emissions. First thing to check on 870 is always EGR Valve, it allows more or less exhaust back into cylinders and need to be accurate to 1% of its movement. Think about it - how big influence on everything its gotta have when - let's say - it allows 50% more fumes than it should and ECM is trying to manage this situation by increasing / decreasing boost or else. Take it off, open it and learn how to deal with this #### device, even if its working properly now (which I doubt) it will fail sooner or later, just go and buy yourself set of EGR Valve gaskets, you want to put it back right, no exhaust leaks !

 

ISX surging is normally an indication of the fuel sucking air. Sounds like you have replaced everything at the engine. See if you find someone with a clear plastic fuel line and put that in between the very first fitting at the engine and the fuel lines from the tanks. See if it is sucking air.

 

If it sucks in air, it will also smoke just as bad and want to stall, which I'm sure is not happening with Vision Logistics. It just surges and probably whistles too sometimes, like mines used to. When the EGR finally kicks the bucket, the engine will spew out smoke and give you power loss as well. Might as well disconnect it and be done with it. I asked Cummins the drawbacks of disconnecting the egr, they said "none" except the check engine light will come on. But you have to disconnect the plug that is hanging there, not the one that attached to the solenoid(or whatever that round thing you see on the egr). Then it should not derate the engine at all. Hasn't derated mines anyways and the other three trucks we disconnected. My trailer is cleaner at the top since the FIX as well. Just my thoughts.

 

Thanks, we've long since tried that. There is air in the return but not in the inlet side.

 

Disconnected the EGR, still surging- no change in symptoms.

 

I read somewhere (since mine is doing it as well only intermittantly), that it is the differential pressure sensor that causes that. Just haven't changed mine yet.

 

Diff pressure sensor? Never heard of that one. Does it go by another name? We've tried replacing several sensors including the exhaust gas pressure sensor. Any idea where that sensor is located? Thanks!