Cummins misfire at cold startup idleing

[Ty]

Hey guys so i cant find a clear answer anywhere. My 03 H/O cummins has had a good amount of work done to it, and last week i replaced the lift pump, fuel lines, and fuel filter…Its starting to get cold up here in ny, but whenever the truck sits for a few hours and i start it up. It will idle horribly, one or more cylinders does not fire off and the truck kinda shakes while the rpms hang around 850. This issue goes away as soon as it put it in gear, but it comes back if its in park or neutral and still cold. Once the truck is warm, the problem leaves. I am clueless, after the fuel system work, it was runnin great, the best it had ever ran. Then one night i went to fill up and then this problem came and hasnt left…Do you guys have any ideas to what this could be?

Thanks in advance!

Topic

[James P Grosso]

Grid heater? Hopefully you did not remove it in one of your mods.

[Ty]

the thing has never been modded, just simple stock replacements…Its possible the grid heater has gone bad and needs replacing but wouldnt i see smoke at startup? The only smoke i ever see is the smallest burp of black smoke at startup and its done that for the longest time, so i dont think thats correlated to this misfire issue? but would the grid heater really cause an issue like this? i mean ill definitely look into it, but ive seen people do grid heater removals and the truck still runs fine but it smokes more than bob marley. And the wierd thing is, that the truck starts up with not a single issue!

[James P Grosso]

When you first start the truck (cold) the voltage gauge will usually be around 12 to 13-volts when the grid heater is on. Put the truck in gear and drive down the street to give it a a good amount of throttle so it builds boost (Heat) and the grid heater should shut off and the voltage gauge should show just over 14-volts.

Hopefully it is not an injector problem, that can get expensive.
I would try a bottle of the Red-line Diesel fuel additive “85-plus”, it does seem to clean pretty good.
Note: the Red line “diesel fuel catalyst” is the same as the “85-plus”.

https://www.redlineoil.com/product.aspx?pid=31&pcid=11
https://www.summitracing.com/parts/red-70802/overview/

[Author]

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