Hi guys,
I'm a regular over at the 48-56 forum and not all that familiar with these newfangled engines. My girlfriend has a 2002 F-150 with the 4.6 V8 and I was going to change the spark plugs for her. She said it started running rough and it threw a code and check engine light. She took it for a scan and they told her the number 5 plug was mis-firing. I'm fairly handy and bought a set of the recommended Motorcraft plugs from Rock Auto, AGSF32PM. It also matched the number in the owners manual so I thought I was pretty safe. Funny thing, when I took the old ones out, they were AGSF22WM's instead. My thinking is they are a colder plug than the supposedly original equipment, but I don't think they've been changed before. They looked well used but the color was good. The truck has about 135K on it.

Long story short, and to get to the question(s), Would there be any reason the factory would have put a different plug in the engine than what is listed? Am I asking for trouble going with a hotter plug than what's been in there (pinging or timing retardation/loss of power)? Has anyone run into this before? Is there a question I'm forgetting to ask? Am I just overthinking the whole thing and need to put it back together and drive it? Any words of wisdom will be welcome. Thanks.

 

If you look in the owners manual, AGSF22wm's are for a 5.4L engine.

If you don't have an owners manual download on here. Owner Manuals | fleet.ford.com

It will tell you specific plugs and gaps for each engine.

 

The engine is definitely the 4.6, not the 5.4. So either the wrong plugs were installed at the factory, or they were swapped out by some idiot along the way. Apparently they worked. I'll just install the ones I have and hope for the best. Thanks.

 

Sure it isn't the COP? The coils are known to fail from time to time.

 

I drove the truck and didn't feel anything wrong, but she was on a road trip and felt the misfire and had it checked out. I had a coil fail on my Mercury Marauder once and it bucked pretty violently, so that experience is what I'm going by. I'm hoping it's just plugs. Worse case, if it's still an issue, the number 5 coil is not too bad to get to.

 

with 135K miles, its time for all new plugs... that being said, 90% of missfires are due to the COP.

 

Just wanted to follow up quick and thank all you guys for your input. I got all the plugs changed and replaced the number 5 COP just to make sure and because I already had it apart. Took the truck on a 200 mile road trip Sunday to visit her Mom for Mother's day and it runs like a champ. Must have done something right. Thanks again! If you're ever over at the 48-56 department, be sure to say hi.

 

Very Good !. Thanks for the update.
is the AGSF32PM the correct plug for the 4.6? or did you do a typo

My manual says AWSF-32P for the 4.6 2002


i thought i read somewhere that the plug changed other than what the manuals state.. Can't find where i read it though.
I need to do my plugs and i am dredding doing it.

 

There was a change in Motor Craft plug designation for this motor some years ago.
Easy to find out by calling a dealer parts department.
Good luck.

 

The plugs I got and were on the list as correct from Rock Auto were the AGSF32PM. ($2.48/plug, btw, half off local retail) In my haste, (and maybe I didn't have my glasses on) I mistakenly read the owners manual as AGSF when it does say AWSF like the example above. While doing my research, I found a website that decoded some of the mystery of all those letters, and it said the W code is half thread and G is full thread. It said you could use a G in place of a W, but can't use a W in place of a G or problems will occur. I saw no obvious visual difference between the old plugs and new ones. That could be the update made to help eliminate the plug blowout problem.