A recent post inspired me to create a poll for the plug loosening issue. Hopefully the results will be interesting!
Please note that the poll is regarding the first instance of an issue being presented. It is not intended to account for repeat occurrences.

If you, like myself, have had to continually manage loosening spark plugs after resolving a loose plug issue previously, that will not be documented here. The poll can only accommodate a single answer per individual.

REVISION: @zcargo informed me of a significant error I made (thank you!!). I've been saying that the dealership print I'd received didn't call for anti-seize. WRONG!


Next time I pass a Honda dealership I'll drop in for another print-out. I'm on the East coast now, so we'll see if it's different

 

Good idea, Señor Pyts. We should have had a poll like this from the beginning of the issue.

 

Thanks, MC! I felt pretty fancy while choosing my words
I don't think I could pull off finding all the old threads centered around loose plugs (this one is brand new) since many were titled with symptoms or like, just looking for insight.

It had never occurred to me why the issue was hotly debated, and until recently I identified it as brand loyalty or just being a butt. However, there was a recent post in a thread, I forget which one, where a person was worried about (I think) the expense of it. I figured that plugs are cheap, tools can be cheap, and advice/instruction is free! Still wrapping my head around the idea that some aren't comfortable or don't have the time. My time isn't worth much, except when cutting labor costs, doing preventative stuff.

I hope more folks show up and participate, even if the data doesn't yield any tangible benefit it might help a person make a decision later.

 

I had a plug eject itself at 67k or so, before I ever replaced.

I replaced them last summer at 125k or so and they all seemed fine.

 

I checked my spark plugs and they were barely tight and the coil packs smelled like gas and had soot all over it.

has anyone done anything special that kept them tight long term/permanently?

edit *clarity

 

I'm sorry to hear about your woes, but I hope you don't get too discouraged! Each person that recognized the issue stated that they resolved it, and each in a reasonable fashion. Different folks had different solutions, but the critique of their peers' methods doesn't invalidate them as thus far I've seen no account over the years where a person had a plug eject after doing their fix. I wish I could now add two extra options to log that information

I'll attempt here to encapsulate the different approaches and reasoning behind them!

torque value:
We've seen increased torque values as one method. A long while back I posted up documents showing that my former local dealership revised the value to a whopping 20 ft.lbs. in contrast to the 14 ft.lbs. shown in the Bishko service manual. Additionally, that was only one dealership, and different dealerships may have different values (I really don't know!). Those that have never had issues would likely be doubtful of the raised value as they may not need it. Edit: It is also worth noting that spark plug manufacturers such as NGK and Denso may list their own torque values on their website. One could also look up a chart of general torque specs based on fastener size, though plug manufacturers will always recommend following vehicle manufacturers' values.

antiseize:
The documentation made no mention of thread locker, **did recommend use of anti-seize**. From what I've seen, most manufacturers of spark plugs state on their websites that anti-seize is not needed for modern spark plugs with their fancy metal platings, but all recommend to default to vehicle manufacturer instructions (so there again is an opening for interpretation.) It's also worth noting that anti-seize functions as a lubricant and thusly affects torque value, meaning that the plugs may torque higher than whatever the wrench is set to. Among the nerds (myself included) there's also speculation about anti-seize affecting thermal transfer between the plugs and their respective holes, and some curiosity about the significance of that value.

threadlocker:
Many have found resolution through use of blue threadlocker. It isn't specified by any manufacturer, so this solution is subject to speculation. Considerations include getting dried bits of the stuff into cylinders when the plugs are removed (significance/solution?), the temperature range of the threadlocker is also a consideration, but again I've yet to hear anyone come back and say that it didn't work. I myself had notable success using no thread lubricant, or copper Spray-A-Gasket (was thinking about thermal transfer and had it on hand) but it's messy/time consuming by comparison to the blue stuff in a squeeze-tube and I haven't heard from anyone duplicating that method. Right now I'm trying nickel anti-seize. (I'm running Denso IK22s, so plug changes are more frequent)

aftermarket spark plugs:
Some folks here run aftermarket plugs (several following recommendations of an old car magazine which claimed performance increase as a result of correcting cylinder hotspots through use of Denso IK22 plugs). Although aftermarket plugs may have the desired dimensions, I've found (though I can't site sources) that there can be small, "machinist grade" variations between dimensions (hypothetical example: thread pitch 0.003 off).
One could easily recommend OE spark plugs and be readily endorsed by the dealerships, but some want the performance mod regardless, and there's no documentation of variance to challenge the idea. Plus, those plugs only last 30k miles, so you'll be back soon anyways!

plug hole re-thread:
Done in cases of ejection, and members have claimed that it totally solved the issue. But doing a re-thread isn't a job for a novice, as errors can damage the cylinder head and cut valves on some vehicles (not sure about the Fit). You can also wind up leaving metal shavings in the cylinder, and of course, there's the question of which type and brand of sleeve to use. So, it's controversial too!

Other considerations: torque wrench accuracy, aggressive driving, warming up the vehicle before driving, average length of trips, ect.

Experience with the job serves to greatly speed up the process and make it less of a concern. For myself, I've gotten removal/reassembly down to roughly 15-20min each. Remembering torque values and socket sizes goes a long way! I also don't mind the fault too much. Whenever my engine doesn't feel or sound quite right I think "spark plugs or valve adjustment". It's a wonderfully short list!

 

how often do you have to tighten your plugs back up? it wouldnt be as bad if the plugs were easy to access like most 4 cyl hondas that take a whole 1 minute to check, but having to disassemble the cowl on the fit every time would be a major pain.

 

I haven't made note of intervals. The plugs get replaced at least every 30k miles, and I have had limited issues in between. Use of anti-seize and/or under-torquing prolly caused each instance (didn't always have the revised spec!). Teaching an "apprentice" has also caused some problems 😂 I'd guess that the best bet would be use of new plugs (because of crush washers) with loctite and the revised torque spec. You could alter your recipe to fit your tastes!

You'll have to choose your own interval that you can live with. 30k, 50, 100, annual, biennial, ect. If you smell fuel, get a weird backfire from under the hood, exhaust drone in idle, notice power loss but haven't hit any curbs, the interval goes out the window anyways. Plugs or valves. Having a manual transmission myself, it's fairly easy to notice. Engagement into first gets extra shakey, or vibration accelerating out of a turn..
One time the car was getting rough, I checked plugs. The little 8mm bolt that holds in a coil for one of 'em had loosened. Sure enough, loose plug under it. I don't know if that's definitive enough to say "just do this whenever you feel like the car isn't running great," but I still check those little bolts. You don't even need to disassemble anything to get to them, and they only torque to around 89 in.lbs ~7 ft.lbs. While the method mentioned may help in detecting looseness prior to ejection, it wouldn't tell you if you were getting coil-killing plug blow-by. It just eases my mind.

As for the anti-seize, yeah, I was kinda absent minded. I'll prolly redo mine dry.

 

Has anyone here had an experience with a loose spark plug(s) that they replaced that did not become loose again?

 

Poll responded to! We replaced plugs around 60k. There was at least one plug a bit loose. Haven't checked since but will soon as valve adjustment is due soon.

 

Bought the 2010 Fit with a little over 100K miles on it. It now has 249K miles and I've never changed the plugs.
Did the original owner do them?....I don't know and I'm not about to take a chance on replacing them with almost 250K miles.

The car runs perfect and I consistently get 40 mpg.

 

I got my fit 5MT (@ 151K KM) beginning of september and it was really lacking low end torque & would hesitate/bog often. I decided to do all plugs and coils, I noticed all mine were pretty loose but figured it was from the previous owner not using correct torque (little did I know what I was in for), found the specs online @ 13/ft lbs and torqued accordingly. About a month later (beginning of Oct) I noticed power loss again at low rpms - googled it & unfortunately found the rabbit hole here. Decided to re-torque the new plugs @ 20/ft lbs. I do get intermittent intake backfires when I blip the throttle to rev match on downshifts, but haven't noticed any power loss yet so hoping the plugs are still tight. I will be ordering IK22s soon and will check to see then if the current plugs have loosened so I can't answer this poll yet

 

Before you re-torqued the new plugs to 20 ft lbs, were they loose again?

 

I did set the torque wrench to 13ft/lbs first to see. I had to move the wrench a little tiny bit before the it clicked so I'd assume maybe lost 1ft/lb in that 4 week period

 

Plugs and valves, valves and plugs I'd consider though, if you put on a more free-flowing intake, reverting to OEM if possible before troubleshooting. Minimizing variables makes life easier.
I'd be more than happy to continue troubleshooting your issue! Oh, some pictures of the plugs when you remove/replace them would be good. If there's discoloration on the threads or the porcelain stem/s, although not 100% definitive, that could give us an idea of what's going on (or what isn't!)
If the threads and stems are clean, plugs likely aren't the problem.

 

I replaced mine at roughly 100k. None were LOOSE loose but i did find some werent as torqued on as others. Nothing alarming that would have made me worry about having loose plugs. Ive put on about 15kmi since then with no issues.

 

Did mine at about 65k with a valve adjustment. #4 was a little loose.

 

Three years ago I changed the plugs and coil packs in my 09. Torqued to 16 ft-lbs.
Yesterday, I checked them and retorqued to 16 ft-lbs. None of them seemed loose per say, but coils 3 and 4 (drivers side) are getting hotter.
The dielectric grease I put on those two coil packs was almost gone from the heat, but the other two plugs were still mostly Vaseline like.
So I'm thinking those two could have been a little loose. My dad thinks it might be a fuel injection problem, unrelated to the tightness of the plugs.
Given it involved the notorious plug 3 I think it was a little loose.

 

It's been stated by some that the valves have a tendency to tighten. I suspect they meant that the valves tighten against the seat (opening less) creating a leaner condition. This could go along with your father's idea, since fuel does pass through the valves rather than directly into the cylinder. Edit: If a lean condition has been created, there should be an increase in the amount of heat generated in the affected cylinders during combustion.

I'd also like to thank everyone here for participating! I'm happy to say that this is a bigger turn-out than expected, and the numbers thus far are really highlighting why there's such division on the issue.

 

I replaced my plugs somewhere around 140-160k. They were in good shape, and none appeared to be loose.