Glad you resolved this before it was an issue... i was not so lucky ( I have a thread on it here)...
I believe the main issue is the 2 different metals, but it is amplified by the design...
These motors have an integrate exhaust manifold (part of the block)... and the main exhaust exits the vehicle right at #2 and #3:

Notice where the exhaust comes out...

This is a pic of my damaged engine... the plug that did not blow out was still snug, but the coil pack showed signs of extra heat...

 

Enzo: Thanks for the pic - FIT's integrated exhaust. That may explain a lot (extreme temps at #2 & #3) since there are so many aluminum head engines and so many other Honda engines out there that don't have the loose spark plug problem.

I'm almost at 70K miles on the car ('11 Sport AT) and 35K-40K on my blue threadlocker fix that kept the new plugs secured.

I need to adjust the valves this summer (no outside work during PA winters) and will check all of my work on the coil packs / spark plugs while the engine bay is open. May also increase the battery to the 51R vs 151R. The start up process is slow enough on really cold mornings that I'll get that "feeling" in the stomach that its a bad day, just before it starts.

 

I know that V6 Accords often have a problem with the #5 spark plug...

 

I wouldn't have believed it but the gas smell was a loose plug. Have changed hundreds of plugs over the years, in iron and aluminum heads, and have never seen this! #2 plug had backed out to the point where the car refused to start. Cleaned the plug, torqued it and the other three to spec and all is well again. Thanks to the forum for coming up with the suggestion! See the discolored #2 coil pack in the picture.

 

My #2 coil pack looks like that as well and the factory valve clearance on the #2 cylinder was way too tight as well.

 

Did you change engines yourself? What did you do? A used one?

 

Lessons learned: 1. Check valve clearance a lot more often than honda recommends to prevent a condition where insufficient exhaust through tight valves pushes the plug out.
2. Periodically check the tightness of the plugs, do not wait untill 148K or some other such number. 2009 Fit? 9 years of service and no one touched the plugs?

This is the issue, Honda is trying to claim the car being maintenance free until 100,000 miles, but we all know it's a marketing hype and blown plugs is of the prices to pay.

 

[QUOTE=spike55_bmw;1391453]

... on my blue threadlocker fix that kept the new plugs secured.

Can you please elaborate on this ^^^.

I am not anywhere skilled enough to even attempt much on a car.

 

[QUOTE=benmaggoswd1;1395595]Literally as simple as applying a few drops of this...



to the threads of the spark plug and inserting.

PS. I'm not encouraging or discouraging the use.

 

Thank you. That's what I was hoping for.

 

I would not use it.
It's not meant for high heat application.

I use a thin layer of anti-seize heat resistant compound with good torquing of the plug.

https://www.f150online.com/forums/v8...g-threads.html

 

I also would not use it but for a different reason. Threadlocker Blue is a good product. I used some two days ago on a fuel pump mounting stud in a steel engine. I am worried that if you ever have to remove the spark plug again which is mounted in your ALUMINUM head, the torque required might strip out the threads. If I were going to try it and I'm not, I would use thread locker Purple.

Just my cautious opinion.

 

I got a used one from the local wreckers... 2012 motor, 40k kms, and then found a mechanic who does work on the side. He has a shop on his property.
$600 for the motor, delivered, taxes in
$1000 for labor.

Still feel like I am driving a ticking time bomb....