Ok, i have a 97 f150 4x4 with the 4.6 in it. I was running the truck at about 60 mph the other night and all of a sudden my check engine light came on and the truck started to chug.I can kick it in the rear and sometimes it feels like all the powers there and then sometimes its a lil chuggy. i took it to AutoZone and ran test on it they said it was showing #3 cyclinder code. I then bought some Lucas fuel injector cleaner and ran through it thinking it was clogged fuel injector.I can hear all the injectors ticking while motor is running. I then pulled the number 3 plug and it looked fine. I put the plug bac on the wire and had my buddy turn my truck over. The plug sparked,that would mean that the wire and the coil pack r good am i right? Next i cleaned MAFS and changed air filters since i was there,it did not help.I also found a bad 25 amp fuse that i replaced.Before i did the the MAFS and the fuse deal,i unhooked my battery.When i was done and hooked back up and started my truck the enigine light was out (no clue why). Can a damage gas cap cause this? also i say chuggish but it could also be defined as sluggish...lol if that makes sense?. Thanks for taking time to read this ramble and thanks for any help.

 

If your #3 cylinder code didnot return, the fault has cleared. What was seen for the code was then old history when it was read.
Rebooting the pcm cleared the code.
The EVAP system has nothing directly to do with the ignition.
Your year has what is called a waisted spark ignition system where two cylinders are paired each for a total of four pairs = 8 cylinders in all.
BTW unless a cylinder's plug is fouled from to much fuel or oil, you can't tell much about how the cylinder is firing by just looking at the plug tip.
Reason: the OX sensors keep the mix on the lean side and very clean burning such that the plug tip will even look like a lean condition (whitish) but is nomal for a FI motor.

 

if its cylinder miss fire, it will probalby return in a day or two. its either the coil or the spark plug... you can have random miss fire and it will ook o.k. when tested as you did.

 

So could the problem be a bad plug or coil pack? Like i said before i checked for spark on well the number 3 plug and it was firing, i did not check drivers side for spark.(will do tomarrow) I have the 2 Coil setup so i just figured if the number 3 was hitting the rest on passenger side was hitting. Today it was like the miss was more apparent in gear at idle and like gassing on it,but in park when no load was being put on it it smooths out a lil. Its wierd how the light came on right as the truck started to act funning and then the next day i test it and says #3cycl then it goes off and still runs like junk.Bluegrass thanks man im not to great with the late 90's and up cars/trucks but im like a sponge man ill soak up as much knowledge as i can LOL. U replied right as i was finishing my reply steve yeah i was looking for the light to come at anytime today but it hasnt so far so Idk man.

 

O.o i see what ur saying steve due to the coil being/going bad it could have been throwing spark to that plug at the time but not to another plug while i was checking them.When the truck started acting up and the light came on and i had it tested what it was is that it miss fired on the number 3 cyclinder first? these r just questions im trying to follow.

 

I would remind that just checking for spark by jump is not a fully reliable way to do it on modern engines.
It's not like having one coil for the whole engine ignition.
The coil paks have electronics embedded in them you can't see.
The PCM uses the coil electronics to select the cylinder to fire in the correct order and circuit 'polarity' as well as handle the high currents and inductive kick control as protection to the PCM..
The muti connector leads are the control leads of this function, the PCM uses.