I've scoured the interwebs and used the search function here, and can't quite find a similar situation as what I'm having.

I have a 2003 Durango with the 4.7l. The issue I'm having is that the engine will run like a top as long as I don't have the fan on(doesn't matter if a/c is on or not). Within about 15 seconds of turning on the fan, the engine starts vibrating horribly and running extremely rough. About 20-30 seconds after I turn off the fan, engine smooths out and everything is good.

There are no codes being thrown, the CEL isn't coming on. I'm at a loss as to what it could be. Maybe a belt? Electrical issue? Gremlins in the motor messing with me?

Any help is appreciated.

 

it is almost definitely electrical, i would start looking for a short in the fan circuit that could be affecting everything else (im assuming you mean the blower fan for the hvac system since you mention turning it on and off, not it going on/off on its own)

 

check the battery bad batteries cause havoc in the durangos