2010 t800 losing power

My dad has a 2010 Kenworth t800 tractor with the cummins 600 isk engine. Recently it has started losing power. It's been to the dealer a handful of times with no real help. Sometimes it runs great, could be for a day, half a day, or just an hour. Then it starts to lose power. It won't turn up the RPMs like it should. It starts out only going up to 1600rpm, then around 45mph the RPMs start to drop off and it can't even pull a load. If it is parked it might run fine in the morning or it might not. It's not showing any codes. Changed fuel filters, no change. Checked the air temp/turbo boost sensor and saw it was gummed up. Cleaned the sensor and it ran good for 2 days, then started acting up again. Replaced the sensor with a new one which didn't change anything. That's where we're at right now. Just wondering if anyone has ran into something similar and might have a lead for what to look into next. Thanks.

 

thanks kaptainkenworth! I'll look into that stuff. what are the ecm calibrations that would help with the egr? probably something the dealer would have to flash?

we did replace the boost/temp sensor after we cleaned it. the new sensor didn't help any..

 

I was just talking with my dad about what you said about the ecm calibrations and he said that the kenworth dealer just did an updated flash on it right around the time this started happening. it was down there for a transmission yolk issue and when he picked it up they said that since they had it they went ahead and reflashed it. he doesn't know what the update was for, if it was off of a Cd or the website or what. I told him to find out more about it Monday.

the last time the dealer had it was running good. the tech had it plugged in and the throttle position went up to 100% like it should. the driver left with it and a couple miles down the road it started acting up. he brought it back and the tech plugged it in and the throttle position would only go to 50-70% . the dealer called my dad today and told him that it had to be the way the driver is pushing the throttle.... needless to say he wasn't to happy about that. you think the random 70% throttle could be related to the new updated tune they flashed or a tps going out or what?

just curious do you work at a kenworth or cummins dealer? I'm gonna try to get the engine sn for you tomorrow. there is a Cummins dealer near the kenworth dealer that were dealing with. thinking about taking it over there.

sorry for the real long post, just trying to get all the information that I can. thanks again.for all the help man.

 

that makes sense. that's actually what it was doing the first time we brought it down. you could move the yolk with your hand so we figured the bearing was bad and the wobble was messing with the vss. they told us that the bearing was good, and that they just tightened down the yolk. my dad is out hauling a load of choose to the mill now to see how its acting. I'm heading up to the shop when he gets back and ill take a look at the wiring and connections. ill let you know what I find!

 

I dug out the paper work from the visit when the kenworth dealer did the reflash, and it was indeed C1110 campaign. We're not sure if they replaced the output nut or not. The truck is going back down to the dealership wednesday for an issue with the high side of the transmission. We've fixed similar issues with other trucks, but figure since its under warranty we'd bring it down and let them deal with it...
We're going to have them check out the vss, connections, and wiring. We're also going to have them bump the "max veh speed without Vss"to 2100 and "vss anti tampering" to high, as you suggested. That way the dealership tech should either find a problem with the vss, wiring etc. And if they don't, we can rule that circuit out if it does act up again. Sound like a good idea?