I have a 2002 f150 4.2 130000 mi, this truck hesitates ( only slightly ) when accelerated quickly from an idel,say at a stop street,or traffic light. It also has a dead miss when in over drive at say 65mph , but only when under a strain , like going up a long grade while slowly accelerating. Mounths ago it done the same thing , the mech replaced the coil and plug wires ,all motorcraft . He said the coil was burnt where the plug wire connects to coil from the back plug on the pass side . When i had a mech look at it last week, this mech said the same thing. Its only been 60 days , what could cause this over and over?

Any suggestions, thanks.........cl

 

When was the last time you changed the plugs? What brand plugs/wires/coil pack?

 

Changed plugs 90 days ago , also new coil ,plug wires all motorcraft from dealer. This is the 3rd time in about 14 mts., also i have ran seafoam cleaner through it ,new fuel filter, i looked for vaccume leaks but im no expert on this.in the past i have had problems with the deal where you turn the key on and get the flashing theft light , but all those coils cant just go bad on their own.

 

To short cut the fooling around trying to find the cause, use a Scanner and do either a trap of the missfire fault or look at the missfire monitors to find which cylinder is the offender.
Then work on the repair.
You need to use a good mid grade scanner and know what your trying to set up or have some one who knows, do it.
At this point your don't know positive what's happening and the cause.
Good shops should know all this but seems they often don't.
.
For example; I cold started my truck yesterday to go out and it was missing. Was ok before this. Run a few minutes then cleared up.
I surmise it was a leaking injector flooded one cylinder over night, but which one? There is no CEL light and code to run with.
My scanner, looking at the missfire monitor records showed cylinder 4 out of all 8 was the offending one 'after the fact'.
What will I do? Likely put some injector cleaner in the fuel as a measure. It has not come back today. Had it happen once a number of years ago.
Good luck.

 

I guess i should haved said this has happend 3 times , every time the mech says the same thing ( different mechs. ) it needs a new coil and the back plug wire on the passenger side is burnt where it fits to the coil. It has been scanned and all 3 times its the same....3 new coils 3 new plug wires, i was shown the coil and wires so i know its really happening , i just cant see what else could cause this.

 

Change the plug in that cylinder, and check the gap before you put it in.

 

There can be an issue with #4 cyl . Coolant leak from the heater hose connection will cause a miss fire on # 4

 

The plug has been changed every time , although it looked new, i also looked for signs of anything leaking,no signs of this , can the obc do this?

 

Don't want to sound stupid , But what is " obc " If you have a consistant issue with #4 , we need more info on what has been done . I jumped here from another , sister site , and would like to help . obc is not in my data base .

 

Back plug on the passenger side on a V-6 is #3, and nowhere near the heater hose. The plugs are down low and exposed, not in wells on top like the Tritons.

 

Mine either ocd is tho lol.

 

You got me ! I read 4.6 , not 4.2 . So , all I posted is null . I guess I need better eye ware ! Sorry , don't kick all my teeth out just yet , give me another chance !

 

Sorry i should have said obd, i am not sure what makes the coil fire when it does, i thought it may be something electric

 

Oh, you mean the PCM (powertrain control module)? Yes, that does trigger the coil, but I don't see how that would cause JUST ONE coil terminal and wire to toast like that, repeatedly. Very strange.

 

Well i will stay on it, i will post what i find it may be of interest to some one or help someone