If you just put new Motorcraft plugs in it with the right gap, I don't see why you should have to change them again. The same goes for the wires. What has me puzzled is , it was like this when you bought it, unless the wires were too close again. Did you ever check the wires on the cap going to the correct cyl ? The firing order, and it's hard to believe the dealer couldn't find the problem unless it just sat outside because they could make more money doing quicker jobs. I have seen that more than once!

 

for emission control it has EGR system, and smog pump. I have not checked the EGR but I will do that tomorrow

 

The scanner is fine; the codes never did change. And I do so HATE to disagree with Hanky, but the 7.5L engine would smooth out at off-idle speeds as its so big. Other then a huge vacuum leak (which would explain smoothing out at speed, but I'd think you'd covered that by now, and you'd probably of heard it, too), I can't think of anything.
EGR could be a concern, but if you monitor the EVP sensor, and it's anywhere around .50V or so, you're fine.
THe inductive backfire was an issue, but as long as the #3 wire goes between 4 and 2 and 5 goes between 7 and 8 on the cap, you should be fine.
Since you could be hearing spark arcing, you might try dousing the engine with water and taking a look to see if there is anything visible.

 

i changed the wires one at a time and dumb as this sounds nope i have not verified correct order and they were bundled together before and i did the same thing....guess i lost sight of the number one rule "kiss" keep it simple stupid!!!! Tomorrow I will ensure the firing order and wire location...also thanks for the heads up on the routeing at the cap...if it continues after wire routing and seperation i will also try the water on the engine.....will report in tomorrow as soon as i get results either way....Thank you everyone for trying to get me thru this!!!!!

 

ok so we put in another set of plugs and wires...routed as instructed and seperated and i am happy to say it is 90% better!!!!! the slight occasional hesitation is still there. I think it is either a wiring or ECM issue though because the O2 mv will occasionally drop from 6-700mv down to 60-90mv then shoot back up to bouncing from 650-780mv. its when it drops off that the mild hesitation will occur...again unplugging the map will take injector pulse width to a constant 6.80 from 4.50 and put timing to 33 degrees and it just purrs but its at 980 rpm. All this is on idle only havent driven it yet since problem got better i will run it tomorrow and see what it does at speeds. All that being said the way it ran before is definately night and day to what it is doing now! Thanks so much to everyone that helped!!!!!!! I hope one day i can repay the favor

 

oh and grease mark the way you said to run specific wires at cap...not at all how we did it the first time....we did however follow your instructions on that this time....Again I cant thank you enough!!!!!!!!

 

Well, I'm very glad I've helped at least one person fix a car. And don't worry too much about the o2 sensor; the PCM doesn't look at it at idle, and if you let it idle for any length of time, you'll notice it stops reading altogether. That's what's meant by the designers use of "jumpback strategy." It runs on look-up tables at idle and then "jumps back" to closed loop at speed.
One other thing to consider is setting the base timing (does anyone besides me still own a working timing light?). Unplug the SPOUT (2 pin connector near the Ign. Control Module, which should be hear the cowl on the the left side near the wiper motor) connector and set to about 10 degrees BTDC.
This couldn't hurt; it can also determine how much slack is in the timing chain...

 

Perfect i will do that Ford said they set it but im not sure it idles at 24....Thanks again!!

 

Thought I would share with everyone that the rv is fixed and runs absolutely great!!!! After setting the timing at 10 degrees the camper ran much better but still had the hesitation to it. I ran a new 4 gauge ground from the battery to the engine block and the problem is completely gone now!!!!!!! Thanks again for the advice everyone!!

 

The moral of the story: perserverance pays off! Good job!