I bought the 2005 G35X Sedan new and gave it to my son with 90,000 miles on it. Now It has 165,000 miles and the engine is missing and running rough. Auto Zone pulled diagnostic code P0302 which is #2 cylinder miss-fire. Since the plugs have never been changed I went and bought six NGK plugs and one ignition coil. After reviewing a couple You Tube videos I dug into the work. After removing everything necessary to get to the coils and plugs I started on the drivers side with #2 cylinder.

I pulled out #2 ignition coil and it was covered with thick gunk and oil. The big shock was that the spark plug was wiggling loose in its threads, 2/3's out of the head threads. I thought that it may have blown out of the cylinder head. But no. It was really lose and came out without needing to use the ratchet!! The new plug went it and torqued down to 20 ft. lb. Then cylinder #4 and #6 were not tight either. #4 needed a minor one handed tug on the ratchet to remove but #6 was loose and removed by hand. All had oil in the bottom of the plug tube so the valve cover gasket is leaking bad. I replaced the ignition coil on #2 plug and the original ones in #4 and #6.

On to the passenger side. All three plugs were barely tight meaning I only needed to do a one handed tug on the ratchet to remove the spark plugs. All used plugs gapped at about .065. New ones replaced and gapped to .043. Cylinder #5 is the only one that did not have oil in the spark plug tube. No, I'm not going to change the valve cover gaskets or the other five coils. The car is about 15 years old and may not make it to 16. It is bumped, scrapped, dinged and generally neglected by the kid. Last month he parked over a concrete curb and pulled the front bumper off when backing out. Since the only repairs and done on my dime and backaches I will spend only what it needs to run right now.

I have NEVER had spark plugs this loose in my 71 years of age. I have not worked on that many aluminum heads but I have got to ask, has anyone else experienced servicing spark plugs on high mileage vehicles that had spark plugs that loose?

FYI - The car is running excellent, the engine miss is gone as well as a ticking sound that has been coming from the drivers side of the engine.

 

I have not seen this either. Normally i'm used to plugs being in there super tight @ 150k+. But i dont come across too many valve cover leaking ones with that mileage.

I understand the whole not spending much money on the car because of its age and etc.

But at this point i would grab ebay/amazon valve covers, they run like $100 and i would do that repair. Because the leak can/will cause another coilpack to go out and you know those coilpacks can run $50 online or $120 in store. To me that is cheap insurance.

 

Typically that only happens if the plugs aren't actually torqued. If you are using anti-seize you should reduce torque to about 15 ft/lbs.