99 f250 superduty 4x4 v10

just to start this off, this truck sits more than it should as i travel for work so keep that in mind.
when i got in it last time i came home it was running a little rough.
i did a power balance with my scan tool and found 4 and 6 were misfiring.\
i bought two motorcraft coils and installed them and it seemed to run fine
i hooked up to my 8.5 x 16 enclosed trailer last weekend to go pick up a fridge (trailer is loaded down with my furniture from my last house) and after initial fluids and tire check we hit the road (overdrive off the whole way)

truck ran fine, drove about 45 min down the interstate to the destination and i shut the truck off
when we left the truck started running like trash again. the sparkplugs were done about 5k miles ago and i checked the gap when i installed them. talking to a buddy he said possibly the cylinder head temp sensor, the MAF or possibly the TPS could have gone bad. its just weird to me that as soon as i shut the truck off after it was running great it started acting a fool. i made it back home and parked it so i havnt been able to check it out but any idea what parameters i can look at to let me know what the issue is? i need to power balance test it again under load to see if it is those same two cylinders or if others decided to go but any other ideas are greatly appreciated.. we all know they are gas hogs as it is, i dont need misfires to lug me down anymore

thanks

 

any ideas would be appreciated, message is to bump

 

Are there any codes stored in the ECM/PCM?

It is possible you have more coils that have gone south. Often it is recommended that you real all coils instead of one at a time.

 

5K miles ago when the plugs were done, did you also replace the rubber boots and springs?
You do realize that the 4R100 trans was designed to tow in OD and only needs OD locked out if it is constantly hunting between gears due to load or terrain. Keeping it in OD more while towing will, or at least should improve that gas hog thirst a little bit. My EX is the dedicated tow rig for our 12K TT and it does all of its towing (46K miles so far) in OD with zero ill effects.

 

The coil packs work in pairs, I have really never had any luck changing one or two or even half of them, I even went a far as changing all of them and swapping out one at a time to try and figure out which was bad, only one came back bad and it was one of the first two I changed. B asically I wasted half a tank of gas and a whole day trying to win, in the end good old ford was the winner.

 

I had the same issue as Fatz29708. Truck sat over the winter and when I cranked it up in the spring, it had 2 codes for misfires (cylinders 4 and 6 if I recall correctly). Replaced those 2 coils and cleared the codes, but truck still ran rough. Drove it a few miles and cycled the key, but no misfire codes. Bit the bullet and swapped the other 6 coils and truck ran smooth as ever.

 

i was in a hurry and didnt check for stored codes honestly, it was running rough and i had to pull my trailer the next day so i just swapped out the two that looked the worst on the power balance test

 

no i did not replaced boots and springs, though i am starting to think i am going to be buying 8 new coils weds when i get home and swapping them. as far as the trans goes, the torque converter is acting up, i tow in od because if i run the truck with the overdrive on it uses the overdrive clutches 1-3 which causes more wear from what ive been told by a buddy of mine who does transmissions . truck has just shy of 200k and PO didnt take the best care of the truck. when towing a load it sounds like the 4r is an 8 speed, due to the torque converter locking and unlocking towing with od on with my trailer which is loaded down right about 7k including the trailer weight. i avg about 9-10 mpg hwy loaded im lucky to see 12.5 -13 hwy unloaded and about 11 city depending on my foot. i will be addressing the torque converter issue at a later date. i installed an accumulator body spring kit which DRASTICALLY improved and firmed up my shifts, but the torque converter is still needing to be done

 

Well i ended up buying another 8 ignition coils and installing them last week..

I removed the ccv hose going to the intake and i found the source of my misfire. The rubber ccv hose that attached to the intake vacuum hose was super loose. to the point that it had enough play to suck air.

after i replaced all the ignition coils i put a hose clamp around that hose and tightened it down. the misfires were taken care of and the truck runs better than i can ever remember it

i hauled about 7k pounds from gainsville to my house in manatee cruising 70 mph the whole way and averaged 10.3 mpg during that trip so i am happy

 

Any chance that you could have dribbled some oil on the valve covers during an recent oil change? That happened to me once with my 5.4. I had occasional misfire. Cleaned it and it was all over.

 

You are in Florida... High humidity and truck sits for long periods of time... Could be getting condensation in the fuel tanks. It ran good on the last trip partially because you probably put fresh fuel in the tanks to make that 6 hour round trip... Might consider some fuel additive to knock the moisture out.

I always enjoyed diving in your area... Beautiful.

Hobo

 

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