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!!

 

Were Motorcraft parts used?

 

No I used bwd coils bwd iac ,ngk tridium plugs . I have a v10 in my excursion and used the same parts no problems ???

 

Warranty #4 and #7 coils and see if misfires improve or you could swap them around and check misfire count in mode $06. Replace the blackened plugs also.

 

I've swapped them around did a fuel pressure test was at 30 dipped down to 29 running at 2000 rpm no load. Gonna pull plugs do a compression test too!!

 

Let us know the results. Add a teaspoon of engine oil for a wet compression test also to see how much the compression goes up.

 

Well 0 compression #4 valve problems I'm guessing!!

 

Burned valve or rocker off its platform?

 

Ya the plug was dry but black so take the valve cover off have a peak.

 

Well got the valve cover off all valve train still in place so the heads coming off!! Any tips??

 

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.

 

I looked piston looks good . I left the evaporator I'm think n just a burnt valve.

 

Curious the mileage on this 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!!

 

Thread inserts need to be aluminum for proper heat transfer of plugs. That may have also caused the valve to burn. So you want to completely repair this head instead of replacing it?