Hi all, I am a bit new to forum posting (good with searching and reading but have never posted) but I am at my wits end! I have a 1999 4.2L with 118K miles. It was riding a bit out of shape and I hadn't done a tune up in quite a while so I knew it was due. As I proceeded with changing out the spark plugs, plug #3 broke off. It broke between the bolt portion of the plug and the sleeve that actually inserts in the threads. I have never seen it happen, but leave it to me for things like this to happen! After researching my possibilities for 2 weeks I found a mobile mechanic to "Easy Out" the plug out of the hole. We noticed after it was out that part of the ceramic and the center electrode was missing. He proceeded to "blow out" the parts through the hole (spark plug 3 hole) by turning the engine over. Pieces of ceramic came out but did not see the electrode. After replacing the new plug in the hole and starting the engine it sounded like a bolt was running loose in the engine. We stopped, took the plug out and turned the engine over again and what would you guess flew out of the hole? You guessed it, the elusive electrode! It wasn't round anymore but all flat! Replaced the plug (the "new plug") and now the truck is running really rough. CEL is on (has been on throughout the process) Bank 1 and 2 'System Lean'. Now the code is showing Cylinder 3 misfire along with the Lean messages. I have changed the spark plug wires and even went back to another (one of the older spark plugs) and while idling the truck is the same. Slightly rough idle in Park at 800 RPM but when dropped in Drive or Reverse it drops to 550 and rough. Does anyone have any ideas of what to check next? I am presuming the worst like a cracked or damaged piston. Any help or direction is greatly appreciated.

 

I wouldn't worry about the piston being broke, I have seen them with screws from carburator plates pounded into them and more, What I would worry about is did it or something get under a valve, suggest you do a leakage test on that cylinder.

Kotzy

 

Be sure to check all your vacuum hoses. There have been a few cases of guys knocking one off/loose during the course of changing plugs.

A vacuum leak can cause just what you describe: codes, rough idle, etc.

Bets of luck and let us know what you find.