Its not just Fits,, Corvettes,Miata, Ford, BMW 3 series and others have had the same issues since Coil-On-Plug technology hit the street.

I interesting thing is the 4 cyl BMW only has this issue with coil ON plug, the earlier cars with coil-per-plug (4 coils with spark plug wires.. ) never had the problem. Its also showing up on a lot of the new motorcycles.

When I've helped build race engines we don't use a torque wrench we use a degree wrench, you turn the plug till it seats then turn the plug a specific number of degrees of rotation.. Based on thread pitch its ALWAYS dead on.

 

"you turn the plug till it seats" — You do this by feel?

 

Thought it might be of interest but my ignition coil and spark plug blew out when I was driving the other day. It's still at the shop, and the mechanic is going to try to replace the ignition coil to see if it has damaged the engine. Fingers crossed it doesn't need the engine replaced. BUT he says this is the third Honda Fit he's seen this happen with. So maybe it's more than just a problem with adequate torque on the spark plugs?

 

The first time it happened to my wife's 2012 it did not damage the threads but it did take out the coil. Maybe it was incorrectly torqued. But on my 2009 it took out the coil and the threads on the head. I can't imagine it was improperly torqued. The dealership kept the pieces to display.

 

Sort of, when you use this method you clean the hole and the plug you apply a small amount of lube and turn it down with a inch lb torque wrench I think it was to 5 inch lbs ,, then you use the degree wrench. I Shoulda been more wordy on that answer..

 

Well, one problem is that the service interval from Honda (2008 Fit) says the plugs should be replaced at 100k miles, but Denso says those plugs only last 100k km (60k miles). Second, spark plugs should not blow out of the head if they are in tight. I do believe there is a torque problem in the assembly plant. Honda does not recommend any service, inspection, etc, for the plugs for 100k miles. So they either need to start checking them before they leave the lot, or recommend a service before then. Or just post a disclaimer saying they can't guarantee the plugs will remain in the head.

 

What if they made the mistake all the way through he manual using Miles instead of Kilometers.. ?? Eek.. Maybe this car is EXACTLY like the old civic that needed everything done by the 60K mark..

 

FWIW, when I replaced the plugs on my GD3 at 100K, the original plugs were nicely torqued down - no issues there.

The coilpack bolts, however, were a different story. #4 - the hardest one to get to, of course - was absolutely frozen to the block. I wound up stripping the head trying to remove it, and three mobile mechanics couldn't break it, either - had to take it in to a shop to get it out.

 

The coil pac bolts are ones I used a dab of dialectic grease on. Just to insure they will come out when I want, and to keep the coil grounded tote valve cover.

 

Each coil has a ground wire (power feed, impulse and ground); bolt is only to secure the coil

 

The hitachi coil packs I got, have a metal liner in the bolt hole and it is part of the metal base plate of the coil pack, so I want those bolts solidly connecting and not have the threads seize to the aluminum. I always found that if all the metal bits have a good clean connection, I have less issues with metal to different metal electrolysis... YMMV..

 

I have an 07 Fit Sport with 200k miles, This is the third time a spark plug has blown out. All were torqued to spec. Right or wrong, I use Nickel anti-seize on the threads. It has taken the coil out each time. The first two times the threads were OK. This time the threads are gone. I tried to install a Heli-coil but its impossible to get too. You can't see down the spark plug hole without a mirror and flash light. Looks like I'll be pulling the head. Has anyone removed a head from a Fit in the car? It looks like it would be easier to pull the motor and do it on an engine stand. I've replaced the engine due to it taking a drink of water though a CAI. This is my source of replacement coils, lol.

 

I've joined the loose-sparkplug club.

Noticed a barely audible 'knocking' or 'putting' sound, only when cold. Sure enough, #3 was loose and leaking. #4 wasn't as tight as it shoulda been, either.

Plugs were installed by me about a year and 20K miles ago. They were torqued to spec.

 

How are your coils look after that? (are they covered by brownish soot?)
I don't use torque wrench when tightening new plugs, the recommended torque is not enough to crush the gasket and retain the plug. The plug threads are very loose on Fit compared to many cars I working at

 

The loose one (#3) had the soot, I'd say it looked the color of a slightly 'rich' spark plug on it's bottom surface. (Which makes sense, as it was probably leaking mostly during warm-up.)
The coating wiped right off with only slight discoloration remaining.

The #4 showed no sign of leaking (coil boot was 'clean') but it was able to be tightened ~ 1/4 turn before I needed to use the wrench. #3 was able to be tightened ~ 3/4 turn before it contacted the seat and offered some resistance.

#1 and 2 seemed fine, they only went at most a couple mm tighter.

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So: if you are removing plugs and see the dark coating under the coils when you pop them off, you can suspect that the plugs were not tight.

 

Exactly!
Were you using anti seize on the new plug treads? I suspect if it's collecting under washer(gasket), it prevents later from making a good seal

 

I'm old-fashioned so I always use a little AS. I only apply it to the lowest 1/3 of the threads...try my darnedest to keep it away from the washer.

With the coil-over-plug setups (where the coil covers the plug hole and keeps it clean) I don't feel the need to blow dirt away as I did years ago.

I only tightened the plugs this time, did not remove. When I replaced plugs at 110K miles, the gaps were only a little wider than spec. Gotta love Iridium plugs!

 

not very reassuring to read this. Buff using AS, torquing to spec, and still finding considerable looseness...

 

The lesson here:


Be aware of changes in 'behavior'. In this case, it was the noise during warm-up. (Our daughter, who is the main driver, never noticed the noise)

I plug security check might be warranted...say whenever you check the engine air filter.


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Loose plugs are sometimes noted with other cars too.. Chrysler 3.3/3.8L V6s are one. And those are iron block pushrod engines. Could the issue be what the sparkplug makers coat their threads with???

 

I've learned in my automotive technology class (back in 1996) to never use anti seize on the plugs going to aluminum heads. In my opinion a thread geometry (less than 60% of the thread height) in the spark plug hole could be a factor