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JimT · 02-22-2020, **(Subject: cm2250 rough idle )**

probably the only lottery i'll ever win.

As for helping, it's just what I do. Of course I got A LOT more to learn when it comes to these trucks/engines. But I like learning new things and I like to share what i've learned. If that helps someone else out then it's even better.

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Picked up the sensors but haven't installed them yet. Looking over the harness I found a spot top front of the engine where it appears to have worn through. Taped it up best I could and haven't had any issues since then. I'll still change the sensors since I got em, but I think the wire was just starting to contact the engine causing the intermittent signal loss. I'll see if I can get a picture in the daylight.

Rawze · 02-22-2020, **(Subject: cm2250 rough idle )**

(02-22-2020 )JimT Wrote: probably the only lottery i'll ever win.

As for helping, it's just what I do. Of course I got A LOT more to learn when it comes to these trucks/engines. But I like learning new things and I like to share what i've learned. If that helps someone else out then it's even better.

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Picked up the sensors but haven't installed them yet. Looking over the harness I found a spot top front of the engine where it appears to have worn through. Taped it up best I could and haven't had any issues since then. I'll still change the sensors since I got em, but I think the wire was just starting to contact the engine causing the intermittent signal loss. I'll see if I can get a picture in the daylight.

where you find one bad wire ... There are usually more in that same location just waiting to fail too.

JimT · 02-22-2020, **(Subject: cm2250 rough idle )**

Did it again this morning. Shut down for about 12 hours last night, started up cold, about 35F just outside of St. Louis. Ran ok for a minute or 2 then SCR warmup kicked in for a couple minutes. AFTER that finished it went back to normal idle briefly before it started lugging? surging? Not sure what to call it. It drops down to about 690-700 rpm for about 1-2 seconds then back up to 725 for 1-2 seconds then repeats. It only does this when the engine is cold and I first start it up, but not every time. Once the coolant temp started climbing above 100 or so it went away.

I don't know what could be going on. This is after I taped up the wiring harness and replaced the main crank speed sensor.

While I had the tools out I also went and cleaned up the DPF doser injector. As I thought, 4000 miles and it was already getting clogged up. Not a lot of soot packed in there, but enough buildup to screw with the fuel spray.

Chamberpains · 02-22-2020, **(Subject: cm2250 rough idle )**

Did you solder repair those broken wires? Sensor wires absolutely need to be fully replaced or at very minimum, soldered.

Your problem sounds like a sensor fluctuating while it warms up. Have you monitored all your sensors voltages using Insite?

JimT · 02-22-2020, **(Subject: cm2250 rough idle )**

(02-22-2020 )Chamberpains Wrote: Did you solder repair those broken wires? Sensor wires absolutely need to be fully replaced or at very minimum, soldered.

Your problem sounds like a sensor fluctuating while it warms up. Have you monitored all your sensors voltages using Insite?

No to the soldering. Best I could do in the parking lot was tape it up so it can't ground out on the engine.

As for the sensors, I've monitored it the best I could and haven't noticed anything that stands out as inaccurate and nothing fluctuating.

hhow55 · 02-22-2020, **(Subject: cm2250 rough idle )**

Mine did the surging, like you describe. It turned out to be hydrocarbons flowing back into the intake, via the egr. Have you tried disconnecting the magic plug?. When I disconnected mine, it smoothed out beautifully.

JimT · 02-22-2020, **(Subject: cm2250 rough idle )**

(02-22-2020 )hhow55 Wrote: Mine did the surging, like you describe. It turned out to be hydrocarbons flowing back into the intake, via the egr. Have you tried disconnecting the magic plug?. When I disconnected mine, it smoothed out beautifully.

Good info. I'll look in to it next time it happens.

Rawze · 02-23-2020, **(Subject: cm2250 rough idle )**

That whole harness (highlighted in yellow) is exposed to rot and bad weather.

JimT · 02-23-2020, **(Subject: cm2250 rough idle )**

(02-23-2020 )Rawze Wrote: That whole harness (highlighted in yellow) is exposed to rot and bad weather.

Yes, that and other spots were the reason I was considering replacing the entire harnesses. Time and money have limited what I can do and when, and most of that has been spent on fixing/maintaining the aftertreatment systems. There are a lot of things that I know I need to address and I'm trying to do them as soon as possible. Part of me is worried that we will discover more things that I'm not currently aware of, but ultimately I'd rather know than blindly guess and hope.