Missfire - intermittent

Futbalfantic

Well-Known Member
Joined
Aug 5, 2006
Location
Charlotte
Triton V8 - '99 F-350 12x,xxx miles
New plugs and half new COP

Sunday I towed my boat to the lake and back w/o any problems. Monday night I get in my truck and start up and take off (with the trailer). Going up a slight incline she shutters so I feather the throttle, give it some more gas and she stalls. I restart the truck w/o any problems and try to go again and same problem. I give up for the night and come back the next day. I drop the trailer and drive around the neighboorhood. No problems what so ever, runs like a champ. So I hook the trailer back up and still a shutter and cant make it up the hill. Drop the trailer again and she drives a 15 mile trip without any problems..... I do not have any ideas where to start any advice:confused:
 
I haven't even started into it yet. I'm going to replace the air filter and the fuel fitler but I'm at a loss of why it would only happen with the trailer, or at random. Seems to me a filter problem would be constant. (it doesnt happen when power breaking)
 
I had a chevy with tbi 350 in it and it would run an drive great until i put a trailer behind it or got into some big big big hills. If i powerbraked it it was fine. It was a weird thing. I would do the fuel filter first and then drive it with the trailer and see what happens then go from there
 
I'll be willing to bet that its throwing P0304 code. Cylinder #4 missfire. Facing the front of the truck its the left rear cylinder. Those trucks have a heater hose that runs down that side of the motor and the lowest point on of it happens to be right over the top of the #4 coil pack. The crimped fittings on the line weap just enough to let the hose leak and it will drip off the hose right on to the coil pack and over time it fries it. Have advance or autozone pull the code. If it's P0304 replace the coil pack. It'll run great again.
 
The cyl 4 COP has been replaced. And with my expereince with the truck is when a COP goes bad it misses everytime not some of the time. I replaced the fuel filter with no luck... could a faulty alternator cause it to do this? Bad ground?
 
The insulators on the coils are bad for drying up and cracking on these, allowing lost spark when it's humid or wet, or just when it feels like it. My understanding is that often these COPs don't fail, the insulators simply fail, which are available separately, but the whole coil is often replaced.
 
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