My E-250 4.2 has continuous miss on cylinder #4, p0304 changed coil pack, wires and plugs, No change. Cats were replaced a year ago fuel trim readings as low as -96.7%' as high as 53.3%. Would a cracked exhaust manifold cause this problem, after replacing coil pack, plugs and wires I noticed the crack between cylinders 5 and 6 on the engine side of the manifold about 1.5" long thickness of about sheet of paper. Here Is a picture of the fuel trim codes.

 

Anybody out there want to take a crack at this?

 

the EGR ports on my previous van V6 were all plugged up, except one cylinder; and that one cylinder had a misfire that was a bear to diagnose. PM me if you want more info.

 

I just stumbled across your post. I realize it's 9 months old.
Did you get it fixed?

Sounds similar to the issue I had with isolator bolts and EGR ports. PM me an update please