Hi guys, been awhile since I needed your help but I'm back. Changed the plugs on my 2001 4.7L a week ago and now it idles really rough and runs rough. Ran smooth before but changed them due to the fact I've had it 8 years and never changed them, thought it was time. You guys have never failed me so tell me where to start. Thanks

 

Right plugs at the right gap?

 

What plugs did you buy? As stated, were they gapped correctly? Did you cross spark plug wires?

 

I think the 4.7 just likes the regular copper plugs like the 5.2 and 5.9 do. No plug wires on the 4.7 to mix up though.

 

That is correct.

The 4.7L engine needs a copper plug to properly ground in the aluminum head. You need to make sure you get the OEM cheap regular copper Champion plugs. You need to gap them at .040 before installation. Of course we don't know which plugs you in fact did install????

5.9L, 5.2L, and 3.9L engines have regular iron cast heads so they have as much of a problem on the grounding end, they just tend to like a plug actually designed to operate in them.