Ever heard of this problem before?

[smudvapor]

When I am driving down the road and it is raining or it is cold and I am running my heater blower on high the engine starts to miss. If I turn the heater blower down the miss goes away immediately and runs fine. I checked my charging system and it is charging fine. Where do you think the problem is? Battery is good too.

 

[adsm08]

Mine does that if the AC is on. I think my issue is in the dis cap, but I haven't tracked it down yet.

 

[RonD]

I would check the voltage while driving in the same situation.
Just hook volt meter up where you can see it to any circuit in the cab.
Fan on high could be drawing more amps than it should, you can test for that as well but really need to do it with lights on, wipers on, and engine at 1,500 rpms

If you can find an electrical diagram find the high speed motor circuit and then see if there is a common power point with spark or fuel injectors, a corroded connector(power or ground) could cause a drop in voltage with fan on high, just inside that common circuit