Was wondering if anyone else has experienced this. It only happens on the coldest of days; when the intake heater grids are cycling, the engine will stumble. There isn't a pattern to it, but it usually does it during those first 4 or 5 cycle events. I mentioned it to the lead diesel mechanic (who I am confident in) at my dealer and he hadn't heard of anyone else with this issue.

 

i have noticed it several times this winter but my duramax did the same thing so i figure it must be normal

 

Are you sure that it isn't just the extra load the alternator is putting on the motor? When the grid heater is on, it draws around 250A of current, so your alternator (probably the 136A) is totally maxed out.
You could actually work out the horsepower the alternator needs to output 136A. Just too tired to do it right now.

Scott.

 

Oh, I'm sure the load on the alternator is where the issue is originating from; I just think it's weird how it impacts the fuel system to the point where the engine takes a noticeable stumble or two.