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I figured I'd create this thread to try to capture any and all loose spark plug related items here.

I've read about loose spark plugs happening quite often in 1st gen MDX's and other models like the TL series and such but didn't really think of it on the 2nd gen until it happened to me.

I'd like to say right off the bat that I've come to my own conclusion that there must be some machining or tolerance defect on these blocks which can cause #5 and #2 spark plugs to back out over time. Because of this, I'd recommend checking them every 15k or so just to be on the safe side. Almost every spark plug/coil is pretty easy to access except #3 which can be a little tricky but still doable by your avg guy.

As per usual Acura's electronics, sometimes you will get codes that pop up that aren't directly related. These would include P1717, P0305(#5 cylinder misfire), P0302(#2 cylinder misfire), 77, and P0401. You will most likely get the transmission error first followed by the EGR error(P0401). By the time you get a P0305 or P0302 error, you can then expect your spark plugs to be only hand tight or worse as was my case. It's really a good thing that the coil plug is bolted down separately to prevent the spark plug from fully backing out. However you will still experience blow by as a result which can play havoc.

From other observations from having a loose plug will exhibit ticking noises which sound like a loose valve adjustment and warmed up idle will sometime feel like it stumbles or misses from time to time. If you are experiencing any of these, I'd highly recommend you check your plugs.

Checking plugs isn't enough though if you already had some blow by or carbon deposits. This is the mistake I made at first. I checked it and the ones that were loose, I just tightened them back up and went on my way. WRONG!!!

If you have loose spark plugs, you NEED to remove them and check for any carbon deposits and/or oily residue, not only on the spark plugs but on the coil pack itself.

Here's why: carbon deposits and/or oil residue will prevent a good electrical contact between your coil pack and spark plugs and you may still get the P030X misfire codes and stumbling even after you tighten down the spark plugs.

So if you notice any, remove the spark plug and clean both coil pack and spark plug with Carb cleaner. It's also important to spray carb cleaner directly into the coil pack conductor where it meets the spark plug tip. This can also have carbon deposits which would act more as an insulator and not provide efficient connection to the spark plug tip. I can't emphasize this portion enough. This is safe to do as everything is sealed on the Coil pack.

Now the other bit is you MUST also check the spark plug boot(rubber piece at the end) for any heat related deterioration on the adhesive which can happen if you have enough blow by from the heat in the engine that turns this adhesive hard and breaks it down. The boot should be on there good and you should not be able to twist it or move it around. If it is loose, you should replace the whole coil pack as that boot will eventually come off the coil pack and get stuck in the spark plug hole and removing it will be a major pain. Ask me how I know. ;)

Typical Codes that come up from loose spark plugs:


All 6 removed. You can tell carbon deposits and oily residue on #5 and #2 plugs and coil packs:


Close up of #5:


Closeup of #2:
 

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Good job. I became aware of this issue from RealWing's engine destruction thread. So I made sure to torque it to spec when the car was 60k miles. (Now my car has 80k miles.) Since I shall replace plugs anyway when it has 100k miles, I don't think I need to do anything else. So I suggest everybody to do it at least once around 60k or 70k miles.
 
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