I apologize if this is in the wrong spot but I didn't see any other spot for it and things have changed quite a bit since I last logged in (July). My dad has a 2001 F150 with the 4.6L in it with an automatic and 54,000 miles on it. After I changed the oil this morning I heard what sounded like a vacuum leak on the passenger side of the engine but it ran fine at that point. Later in the day he called me and said that it was running terrible, skipping, sputtering, and it even stalled once on him. The only code it's showing is the P0353 and from what I've read that narrows it down to the number 3 coil. Since its a COP setup does that mean its on the number 3 cylinder? I'm think it's either a bad plug, a bad coil, or a bad ignition wire? What do you guys think? Any input would be greatly appreciated. Here are the other symptoms: rough idle but gets better as rpms increase, rough while driving (truck shakes slightly at cruising speeds in OD), shake stops when accelerating at 3/4-WOT but surges (seems like it's being held back then gets to a point where its not and almost jumps ahead), also the SES light is not always on when its acting up, actually the only time I could get the SES light to come on is when I cleared the code, shut the truck off, restarted it, and then revved it in Park. If I just let it idle the SES light woudn't come on even though all the symptoms were happening. Sorry for the long post but because of a very busy weekend this is the only way I have to try to figure it out. Thanks again for any help/input.

 

Check that the coil plugup is on securely.
It should snap-lock in place and not just slide off.
The code is for primary circuit failure, not a plug or coil 'missfire' since the computer sees it as a electrical failure and not a cylinder failure.
#3 is the third coil back on the passenger side.
Good luck.

 

Thank you for clearing that up for me. That makes sense since the noise is coming from the passenger side and also why the SES light doesn't always come on. Thank you again.