Hello there I am new to this forum and have a problem with a 04 4.6 in my f150 , it has a noticeable knock at around 1500 rpm under slight load kinda shifting into overdrive .This knock goes away when you step on it and does not happen all the time . Today though it started running rough and I would say misfiring When it started knocking this time but cleared out.I cleaned maf and throttle body , changed the oil and filter all motor raft vehicle has 81000 on it and has been well maintained does sit a lot as I have a car for commuting . I have read some threads on here but do not seem to see anything similar to this problem , I have some limited mechanical knowledge and was wondering if a coil pack would knock or did a coil pack happen to go because of this "knock" or a plug ,again no code .I have owned since new and have a edge programmer on the tow setting for a few years now truck runs very strong and idles perfect , has no knock or unusual noise at idle. Any suggestions would be appreciated....thanks

 

Spark plugs and possibly coils. With 81k, if the plugs are original it's time. You are probably hearing spark knock. When you get it tuned up and no longer missing, if it still knocks you can either use higher octane gas or return it to stock and ditch the Edge.

 

Thanks glc for the reply ...i was kinda leaning towards that as it has no noise at idle as some members describe cam phazer or cam sensor noise , i just didn't know if a bad plug or coil would make a knock like that ...but for an instant today it bucked and shuttered like a coil when it started to knock .I have changed 2 coils on this engine through the years only thing that has ever bothered,just no code this time and sometimes just won't do it ..thank's again for your reply

 

The 04 4.6 doesn't have cam phasers. so you don't have to worry about that.

 

Thats good new's ,one less thing to try and figure out ...is this one of the engines that are prone to breaking plug's by the way?

 

No, it's one of the ones that can blow plugs out. When you replace them, use Motorcraft plugs, NO antiseize, and torque them to 28 ft/lb.

 

thanks glc have not had time to work on it but today it started knocking again and this time had a misfiring fit and backfiring finally spit out a code of po352 so i hope thats what the knock was ..when i get it done i will post results here

 

I would replace the plugs and coil boots - and #2 coil. Second one back from the front on the passenger side.

 

that was some good info ..just changed all the plugs in itand the coil for #2, that #2 was not even tight kinda backed out some, also electrode was completely burnt off nothing left ...don't even know how it was firing ,that must have been the knock because i took it for a spin and quiet so far ...changed fuel filter also ...ran a little roigh at first but straightened out ...thanks again

 

Put a bottle of Chevron Techron or Gumout for high mileage engines in a tank of gas just for fun.