spark plug backing out

My center spark plug on the drivers side of my v6 has backed out for a second time. what is the recommendation torque for the spark plug? Is this a common issue on this motor?

 

Torque is something like 12 or 13 lb ft I think. Best method is hand tighten to snug, then quarter turn more. Has someone stripped the threads on that bad boy?

 

They don't appear to be stripped...thanks for the info

 

The threads in the block - hard to inspect but if you can, do they look OK?

 

I like to pre-crush the fire ring sealing washer on the plug. It helps a ton on the "feel" of tightening your plugs and saves your alum head from stripping out that critical threaded hole. Without pre-crushing, you are trying to feel for the plug to get tight,,but it kinda doesn't due to crushing that ring as you tighten so one keeps tightening the plug waiting for it to cinch down.

WHOOPS!,,too tight,,you are now learning about heli-coil inserts and that whole procedure.

Pre-crushing that sealing washer allows the plug to run down and snug immediately,,then your 1/8-5/32 turn seals the plug to the head and you can feel good about it. No torque wrench needed.

Yes,,the pre crushed washer still seals up just fine. Been doing this little trick for many many years without leakage at all.

If it has backed out for a second time,,I would say the previous owner? got a little excited when installing that plug some time in the past, and might have worked those ALUMINUM threads a bit too much.

Another problem is that the sealing washer was put on upside down. the rounded/tapered side of the washer goes against the head, and the flat side goes against the flat base of the plug. Bought 8 plugs for a project car with alum Dart heads. 4 plugs out of there box had the washer on the right way,,the other 4 had them inverted the wrong way.

Find a grade 8 nut at Ace Hardware that fits the plug threads. Mount the nut in a bench vise, run the plug down and crush the washer. Remove from the nut and install the plug. It's a good habit to get into.

 

Thanks guys I really can't see the threads in the head....but I will check that ring on the plug. Thanks for the tip!

 

I had this problem today. I noticed a knocking sound on my 2003 3.4l with 267,000mi, when I opened the hood I saw a gap between the valve cover and the ignition coil boot(where the knock was coming from). I was trying to figure out why the ignition coil popped off and I couldn’t put it back on. After searching here I realized that the spark plug backed out. I tightened it up, the knock is gone and running smoother.