Hello I just changed 4 spark plugs in a 2008 5.4 I got 4 changed with only 1 breaking. I was able to get the broken one out with no problems I blew out the cylinder and stuck a magnate in to make sure nothing fell in. Before I changed the other 4 I tried to start it and it didn’t want to idle and the started knocking like it was about to blow a rod. I don’t know what to do now any help is great thank you

 

You sure you got the right plugs? 2008 was the year they changed to the one piece plugs, could have got the wrong plugs, and the piston was hitting the spark plug.

 

Maybe something is still in that cylinder. Take the plug out where the original broke and see if it is all beat up from plug debris. I doubt the pistons are striking the plugs because once the gaps are gone, it will stop running.Did you try a shop vac to get any leftover plug debris out?

 

^This. 2008+ 5.4s used a shorter 1 piece plug

 

Yes I used a shop vac. I took the plug back out when the old one broke and the ground strap is bent. Could it possibly be a bent valve that’s hitting the spark plug? I’m lost at this point

 

If the ground strap is bent on the new plug when you removed it, something hit the plug, could be a valve, could be the piston. The only way to find out, is to run a camera down that cylinder.

 

If the engine is original, your 2008 uses the Ford SP509 plug. I hope you didn’t install the older style, which stopped being used in October 2007.

 

What plugs were used has never been verified for some reason.