08 F450 6.4 smokes after 4 minutes

speedracer77 · Mar 9, 2026

I have an 08 F450 6.4 that starts running rough and smoking after 4 minutes run time. It starts and idles fine, then around 4 minutes the idle goes rough and it starts to smoke badly from the exhaust. If I shut it off and restart right away it's back to running fine. Does it again if I leave it idling. If I put my foot into it to warm it up and smoke out the whole neighborhood it stops smoking and runs fine once it's warmed up. I am thinking the EGR starts to open then, and when I shut it off it resets, so maybe there is coolant leaking internally in the EGR coolers? Had the EGR housing off and the gunk buildup seemed pretty damp and soft. I'm a gas guy so I'm used to EGR soot being dry and crusty. Is that normal for diesel?

6.0 Tech · Mar 9, 2026

What color smoke? White/gray would indicate coolant, blue is oil, black is fuel. Although white could also be fuel, but it’ll have a very different smell than coolant. It could really be anything from a bad frp sensor, to a leaking injector, to a turbo issue, or anything in between. A blown egr cooler should smoke at all times, as if it’s not going in the engine, it’ll be going out the exhaust. Is the truck stock? It could’ve a bad cat, and it may be trying to go into regen

DEEZUZ · Mar 9, 2026

Does this have a history of gaining oil? If so, take loose the lower charge air boot and see if any oil comes out.

This sounds like trucks I've had that the cac had more than 3 qts of oil in it. They will eventually run away

webb06 · Mar 21, 2026

DEEZUZ said:
Does this have a history of gaining oil? If so, take loosen the lower charge air boot and see if any oil comes out.

This sounds like trucks ovebahd that the cac had more than 3 qts of oil in it. They will eventually run away

Seen this before as well. Drain intercooler. Or drain oil and see how much excess you get.