Hi guys I have a 2002 f350 changed all plugs and have a misfire on cylinder 4 at 1300 to 1800. Pulled a 30 ft travel trailer 2500 to 4500 rpm no codes. I swaped injectors and no change. #4 plug was black and all others were good. Any ideas?? I changed iac ,coils ,o2 sensor,checked for intake leaks .also now and then #7 kicks up also?? Help me please!!
Did you take the AC evaporator box off to remove the valve cover?
Borrow a bore scope and look in the cylinder through the sparkplug hole. There may be a hole in the piston. If you do not have access to one put #4 on TDC and pump compressed air in and listen for where it comes out to know where the hole is. Resealing head is difficult on a Modular. If piston is damaged you would be better off installing another engine.
If head is reusable use the "special service" Motorcraft head gasket and clean mating surfaces with a plastic scraper and metal surface prep fluid. It will be difficult to install head in chassis without scratching it. Install new timing set.
Has 70,000 miles on it. I'm the second owner but I got it from a friend.it had a bad helli coil repair and burnt two plugs off!! I repaired the hello coil but still had the misfire.has to be the exhaust valve cause the plug was black but dry.im hoping!! Not much room to work that for sure!!