My engine is misfiring in cylinder 3 on a 4.2L v6. I was wondering if anyone has any idea what might have caused this. And if this is the cause of the stumbling when i accelerate?

Any help would be appreciated Thanks

 

Most likely the spark plug or the coil pack.

 

when was the truck last tuned up if ever? i'd pull cylinder 3 spark plug and look at it.

 

I changed out all the spark plugs and the spark plug wires though

 

i'm not so sure about the 4.2 but the 4.6 and 5.4 are picky about the spark plugs and wires(4.6) that you use. swap the #3 plug with #2 and see if the misfire moves. if it doesnt then try swapping #3 injector with #2 and see if the misfire moves then. i'm thinking coil pack tho.

 

If plugs and wires check out, try unplugging the EGR valve vacuum hose, and drive it. If the miss goes away, you need to pull upper intake and clean the EGR ports in the lower intake. Common problem. All ports clog except one, and all EGR flows to one cylinder. I've been bit by this on a couple of occasions. This is only on the 4.2 engine in trucks, and the 3.8 in cars (after 95)

 

stumbling when you accelerate could also be your fuel filter

 

It was just a coil pack in my truck..

Thanks