So it finally got cold enough to kick on the 3 cylinder high idle. After it runs for about 5 minutes I noticed that it intermittently switches to 6 cylinder high idle. I've had high idle for 3 years and this has never happened. When it does it it only does it for a second or less then it goes right back to 3 cylinder. Once it starts it does it 5-10 times per minute. I have searched on many forums with no findings of similar symptoms. Wondering if anyone has any idea on possible causes or has seen any threads with info on the topic.I'm going to attach a data log from quadzilla. It happened multiple times here 

3cylhi.csv

Here's a video, can slightly hear it

Hi.mp4

The truck is smart enough to know if the truck is struggling to keep 1200 rpm in 3 cyl mode and it will kick out of 3 cyl into 6 cyl.  

 

This happens to me when the truck is cold cold and the vgt is in warmup mode.

It has never done it before(although has been overhauled and new injectors since last winter) and its only a blip... Also only does it after starting to gain temp and run well not right off the bat when it's struggling... Did you happen to watch the video @Me78569? 

thats very odd.  

Alternator loading? My does off and on where the grid heater hit and it stuggles to keep going against the exhaust brake. So I'll start out on 6 cylinder and flip over to 3 cylinder later. Or start on 3 cylinder and wait 5 minutes and the add exhaust brake. 

Its only a blip of a cylinder coming online.  

My truck did this Christmas Eve morning as it was -11 F that morning when I started it to leave Colorado. It fired and shortly after as I walked back into the house it went to 3cyl it was like the anti-stall kicked in...quick rev on all six cylinders to keep it running and back to normal and 3cyl warmup. 

If you watch you'll see the grid heater kick in about the same time the engine struggles and bounces out of 3 cylinder mode and revs back up on 6 cylinder mode.

12 minutes ago, Mopar1973Man said:

If you watch you'll see the grid heater kick in about the same time the engine struggles and bounces out of 3 cylinder mode and revs back up on 6 cylinder mode.

That's exactly what I figured happened. 

1 hour ago, Mopar1973Man said:

If you watch you'll see the grid heater kick in about the same time the engine struggles and bounces out of 3 cylinder mode and revs back up on 6 cylinder mode.

This is not the case. It will do it only after running just fine on 3 cylinder for 3-5 minutes, then is random, not in concert with grid heater cycle

2 hours ago, Me78569 said:

Its only a blip of a cylinder coming online.  

Exactly, you can hear it in the video I posted.. It only does it for less than a second

Are you running a Quadzilla?

he is.  

 

the can fuel ing message is disabled at idle though, unless quadzilla high idle is active.

 

 

maybe tps is flicking on and off?  

I've seen where Quadzilla flops timing enough that 3 cylinder mode is running on 1, 2, and 3 cylinders. Remove the Quadzilla and it goes back to 4, 5, and 6 cylinders for 3 cylinder. Don't know why but it does switch it.

you know what it is, it's the check in place to decide to fuel or not,  If rpms are above 1200 the quadzilla may trigger.fueling.  this is in place to allow timing adjustment nad fueling adjustment for trucks with Fly by wire CC.  


I can fix it if it is a big enough issue to warrant.

 

6 hours ago, Me78569 said:

you know what it is, it's the check in place to decide to fuel or not,  If rpms are above 1200 the quadzilla may trigger.fueling.  this is in place to allow timing adjustment nad fueling adjustment for trucks with Fly by wire CC.  


I can fix it if it is a big enough issue to warrant.

 

Honestly if it isn't going to hurt anything or runaway I don't care. Just was nervous could be vp,ecm, or injector issue

Nope it is literally the quadzilla being 1 piston behind thinking it needs to fuel some.  

Yup also explains why it doesn't happen for 5+ minutes.. Warm up mode set to 120ºf