I mostly notice a misfire, in fact several as I'm cruising up hills etc. So I'm trying to trouble shoot this.

My plugs are about 2 years old, the wires about 8 years old. The only thing it may be are the coils that are original. I did get a 305 code regarding the misfire. My truck is a 1997 F150 with the 4.6, 166k miles

Is it possible the coils are bad? If so, is there a test I can do to check them?

Thanks.....

 

had same problem in my 4.6l 97 f150

turned out wires were bad
change plugs and wires

 

I just had this night mare ,the auto shop changed every thing possible turned out it was a plug issue. Use motorcraft plugs save the head ACH

 

me too new plugs and decarbon the tb, 2001 4.6

 

How many *miles* on the engine, wires, and plugs - and what brand of plugs and wires are on it?

 

I've got 166k on the engine, the wires where replaced by the Dealer (OEM, 8mm) while under warranty when the engine had about 15k miles, the plugs are Autolite Platinum AP 104 with about 52k miles on them.

 

P0305--#5 cylinder misfire. Culprit: Autolite Platinum Cure:Motorcraft. If the dealer replaced wires with OEM wires, don't worry about them, if they don't say Motorcraft, replace them too-- or you're going to be seeing a lot more codes like PO301, 302, 303, 304, 306...get the idea?

 

166K on the eng and they were changed at 15k do the math-----

change the wires and plugs

the wires can "leak" run the eng in a dark space and watch for sparks

 

I put Autolite Plat's in 8 months ago. In the last couple of weeks,maybe the last month, I have noticed a change in power, mpg's, and a slight misfire now and then.
This weekend, I'm installing Motorcraft Dbl Plat's with new COP's (Global Automotive's from Ebay).
The Autolites lasted a whole 5000 miles.
I wish I was a member of this forum 8 month's ago, I would have found out that I should use Motorcraft only. It cost me 32.00 and 1/2 day of labor when I did it. Lesson learned !!!

 

Yep, time for plugs and wires - and make sure you use dielectric grease. Motorcraft plugs and wires, please. If you still have issues, then look at the coil packs.

 

Your running Autolites for one. Not Ford spec and she won't run right until it has the plugs that were engineered for it, back in there.

Look at the stickers under the hood (on the cowl) - Tells you what to use.

Pick up some fines wires (Motorcraft Plugs) / Motorcraft wire set/ dielectric grease and have at it.

 

Your lucky, mine lasted 40 miles

 

Looks like I'll tackle the plugs 1st and go from there. I'll def use the Motorcraft AWSF-32PP (stock OEM). Now the plugs are the AGSF-32-FM "finewire". I think these plugs do replace the former AWSF prefix plugs. Now they are threaded all the way up to the tapered seat. Will the full threads be an issue?

Thanks for all the great feedback.....