Engine/Transmission (1998.5 - 2002) Stumble/misfire when up to temp.

[ROADWARRIOR]

Looking for opinions. I know a lot of people have this stumble or misfire when the temps are cool out. I haven't found a definite fix in the search feature either. Mine has done it the last three winters when it gets below roughly 40. It will start up and idle fine. I'll drive for a while and then I have a miss that is not constant in rhythm.



Well today, it was in the mid 50's. It started up fine and I drove for 30 miles. During cool down, it had a pretty bad miss. It sat for an hour and a half and when I restarted it, it sounded fine. Drove 30 miles back home and it had the worse miss that it has ever had. It wasn't firing on all of the cylinders continuously, like when you first start it in sub zero weather. It was shaking the whole truck and did it up to 2500 rpm in neutral. No smoke at all out of the stacks. So I pull it in the garage and it was idling fine.



Start it up this evening to come to work and it sounds good. Get to work and it is back to the more normal intermittent misfire during cool down.



Sorry this is so long, I just never read of anyone having where it wasn't firing on a cylinder continuously. Cummins is of no help. I sent them an e-mail earlier this year and they said it was the grid heaters. lol I have good fuel pressure and the box was not on at all the whole day.



Thanks for any help,

Dan

 

[ROADWARRIOR]

BTW, no check engine light either.



Dan

 

[DavidC]

FYI, if the wires are still connected to the box it is still in the system. The only sure way to eliminate the box as the culprit is to return all wiring to stock.



Dave