Injection/Pilot injection rattle

[08lmm72mm]

My truck is giving me some injection rattle issues while at hiways speeds in the 1600-1700rpm range. The rpms with go up/down about 30-50rpms while staying the same speed with the cruise control on driving on flat hiway under light throttle. As soon as there is a good headwind or incline and the motor is put under more load the rattle goes away and its smooth as can be. It almost feels like a rough u joint but isn't. I talked to Mark about it awhile ago and he said some LMMs have this issue and he got some of it tuned out but its still there. Ive attached a log you can see at the start of it where it rattles with the pids i have then when it goes smooth is when the truck starts to go up an incline.

Will someone with some tuning knowledge beable to look at my log and point in the right direction on which table in the tune to adjust? Id get Mark to do it but i believe hes done now correct?

 

[2004LB7]

It's almost always timing that causes it. Sometimes you can get it if the pilot timing is pushed too far out by modifying the main timing.

I haven't looked at your log yet, as I'm on my phone, so what kinda timing, pilot and main are you running at that ratting RPM?

Also, did Mark leave the tune unlocked? How where you expecting to fix it if he wasn't going to do it?

And one more. Injector rattle to me doesn't sound like a u joint at all. Or at least I can hear a big difference. Injector rattle should be quite recognizable. Definitely make sure it's not something else if you are not 100% on it being injector rattle

 

[08lmm72mm]

Yes it has to be timing. Only looking to modify where it happens. This doesn't have a sound to it, just feels makes the engine jump rpms +-30/50 rpm. Mark says it pilot injection rattle and he calmed it down so I believe him.

 

[PureHybrid]

Is the converter not locked at this point? 50rpm would make it buck pretty good

 

[08lmm72mm]

Converter is locked yes

 

[2004LB7]

Sounds more like the converter clutch is slipping if you get RPM change. Timing rattle won't change the RPM

Try logging converter RPM slip

 

[08lmm72mm]

I logged converter slip it isn't that. Clutch stays locked. It's a Limitless 1078 with very minimal miles on it and no abuse. I can go wide open throttle on any tune and it locks and no slip. This issue is under very light throttle with little load on the engine. Mark said some LMMs have this issue. I don't think it happens to other year duramaxs.

 

[Chevy1925]

You didnt log mPa (actual rail pressure) so its hard to say exactly where the uS is in the tune but you can drop another degree out of main timing and still be ok. try pulling 1 or 2 degrees out in that area and see if it stops. you can move pilot up and down a few degrees as well and see if it helps. just do one change at a time.