Hi all! I know this topic has been beaten to death, but I would like to share my experience and urge you TL owners to CHECK IF SPARK PLUGS ARE TIGHT!

I honestly came across a bunch of posts on AZ about loose plugs and what not a while ago and it didn't appear to me to go check it myself. Totally slipped my mind

I have a 07 TL-S and was driving home the other day on highway and around 2K RPM / 60 MPH ish, my engine light was flashing on dash, I felt rumbling and assumed I was having a misfire but it seemed okay once I gave it more gas. Made it home, and it was a big shaky during idle. Didn't think too much of it as no codes appeared and engine light on dash was not present. Later started her up and during idle, I got a P0303. I shut her down and went to check the coils. Removed the engine covers for access and when I took out cylinder 3 coil, it had oil on it and was melted at the tip/boot. Boot was stuck around spark plug and I do not have much tools. Drove my second vehicle to advance auto to buy a scribe pick tool and got the melted boot out. Proceeded to remove the plug and I put 2 small extensions together attached to the spark plug removal socket. The spark plug was LOOSE and it came out with little effort with my hand spinning the extensions. I went on to check ALL my plugs. Believe it or not.... plug 4 and 5 were LOOSE and plug 5 had a tiny bit of oil on it. All other plugs seemed tight.

I thought I was in the clear when I was trying to install a new plug, but the new spark plug would go hand tight and then with just a tiny more strength of hand tightening, it would spin all over again as if I was putting the plug in for the first time. I had never dealt with anything like this so I thought OMG..... maybe the threads are cracked so no matter what the plug will just spin and spin. I was so worried I couldn't focus on anything else besides trying to find someone who would help me.

I went to a mechanic shop that I have been to before and this particular mechanic pays attention to the little details which is why I chose the shop. He told me he would be able to fix it without removing head and said it would take a bit longer because it is cylinder #3, firewall towards driver side. He called me today and updated me, said he tried to tap the hole but it was a no go. So he proceeded to make a bigger thread and said it should be ready tomorrow. He checked the internals, but wants to check again for shavings before he closes everything up. Like I said, attention to detail and whatnot. He also said this probably happened because who ever did it last most likely did not torque them. I have a service record from the previous owner who got plugs replaced around 104K. It current has 125K.

I think it could of been much worse from what I have been reading here on AZ as other TL owners reported. If you have not done so just please check your plugs before something similar to my case occurs. I don't know how much the cost is for everything, but this particular mechanic has given me labor discounts in the past in the amount of 50%.

Attached are pictures of the plug, coil pack, and spark plug hole.

 

actually there are several cases where member bought the car as CPO and 100% sure that no one has done 105k service and yet the number 5 still loose. I bought my TL at 59k miles and changing the plugs around 86k miles, not a single one of them were loose. I am pretty sure my hand tighten is way over that 15-19 Foot pounds recommended.

 

Service manual procedure is 13.1 ft-lbs with anti-seize. NGK recommends 18-21.6 ft-lbs and no a/s.

OP, I can almost guarantee that whoever did the 105K maintenance probably didn't use a/s and did not torque sufficiently. Glad it's a fixable issue for you