I have a 01 F-250 w. a v10 that used to have an engine knock/slap at idle that was louder cold than at oper. temp. I just thought it was a worn pin and/ or piston(engine has 230,000 + miles). So it comes time for a plug change (every50k since new). Changed the plugs and the noise dissapeared. Any ideas on why? All the old plugs came out fine and looked normal. Except for the back driver side. It seemed not quite tight enought w. resistance. I worked the plug back and forth w. penetrant and couldnt see any aluminum on the treads.Plug looked like the others.

 

It was the loose plug. You are really lucky that you caught it as myself and other members I'm sure can verify the high cost of fixing a plug blow out.

 

Well the weird part is it had been making noise for about 1-2yrs, started faint and progressively gotten worse. I pretty much had gotten used to it and didnt worry too much becuase it went away when the engine warmed up.I checked my maint. log and 2 yrs was about 30k miles ago.

 

I hear ya, I chased it for awhile as well. It got the better of me and Im a professional mechanic, hard to admit