Recently bought new 12 6.7 cummins, during Canadian cold winters -20c- -30c as of lately when I start truck up and it goes into high idle it will stay at say 1200 rpm then have a little surge almost fall down in rpm and then come back up, it does that continuously until I drive away seems ok once I am driving. This is brand new 1300k dpf delete with h&s minni max tuner. I was a 5 year duramax guy before the dodge, and new to dodge scene, not totally new to cummins as working on case IH farm equipment is cummins equipped. Is this the grid heater causeing that much parasitic drain on engine? Is this normal?

 

Sounds like grid heater to me. See if RPM drop coincides with volt gauge dropping.

 

I live in Central Maine and have a 2010 2500. When I start mine in the winter, I believe it high idles at 1000 RPM. I do notice my voltage varying as the manifold heater kicks on/off for the first several minutes. But, the engine rpm does not vary that much as the heater cycles.....maybe 50 rpm...maybe less...it's barely noticeable.

Could this be a small fuel/gelling problem?

Maybe some of the more experienced diesel guys can offer advice or insight.

 

Its just your manifold heater cycling guys. No worries. Here in a couple months it won't do it anymore.