This one is stumping everybody. I had the original factory COP's but was getting that popular 4.6 liter hesitation. I changed out the plugs first with Autolites. The hesistation was still there. I purchased new COP's from Global Automotive, as well as Motorcraft plugs. After I put the new COP's and new spark plugs in, I started getting a loud knocking, sounds like it is coming from five or six. 1-4 doesn't sound like it has a knock. So I changed back to the autolites with the new COP's. Knock was still there. THEN I changed back to the Motorcraft plugs with the old COP's. The knock is still there. Anybody have any ideas on what the knock is from? I have all my sockets, so I know none are in the block.

 

When you removed the old spark plugs what was the condition of the engine? Hot or cold? When you put the first set of plugs in did you torque them or just snugged them down?

 

The engine was cold. When I put the plugs in, I hand tightened them first, and then a quarter turn with the ratchet.

 

Sounds like you put the plugs in correct. The other thing I would look at is a rocker arm problem.

 

This happends when the EGR is leaking as well - Teflon tape the nut if you took it loose - if not , count your sockets again .. Pull the plugs , stick a magnet in there first then suck the cylinders w/shop vac (could be a stone that didn't blow out of the plug chamber last change..).

If you end up pulling the pan you have to take the pickup tube/screen off. 10mm ratchet wrench works best..

Good Luck.