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Discussion Starter · #1 ·
Hi MDXers,

I tried to replace the spark plugs on my 2004 MDX at 190K miles. I didn't realize any issue before the change, and the engine ran strong (kinds of). I got average 19 MPG. The engine had the click noise which called for the valve clearance adjustment service. I decided to replace the spark plugs before that service.

Thanks to anyone who contributed on this website, and the process went much easier than I thought.

However, I did have problem with 2 plugs:

1. The rear passenger one
There were some oil on the coil, even not terrible.



2. The front passenger one
This one was is bad shape. The coil was a little bit more difficult to remove than the other 5. When I eventually get it out, the pole of the plug also came out. The coil had lots of dust/rust which seemed the result of burn?





So my questions are:
For the rear passenger coil with oil
  1. Can I reuse the coil? If so, do I have to clean out the oil and how?
  2. There may be some oil in the plug well. Do I have to clean it out and how?

For the front passenger side plug/oil:
  1. Can I reuse the coil? Any good way to clean it out?
  2. How could I clean out any dirt in the plug well, before replacing the plug?

Really really appreciate any help!

Sorry the image links don't work. So I re-attach all the pictures here.
 

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First, I'd suggest looking at the high-pressure power steering line (that happens to run more or less over that oily plug). I'm betting you have a leak in that - or possibly, in your valve cover. If you don't find a leak in the power steering line (run a clean paper towel down it and see if it gets wet), then plan on replacing the valve cover gasket when you do adjust those valves (please do that ASAP - 190,000 miles without it is WAY too long).

If it was me, I'd clean out the oily coil using electronic contact cleaner, but you can probably get by with brake cleaner or even denatured alcohol. Chances are if it was running OK before, it'll be fine after cleaning. Just find the source of the oil or you'll be doing it again (and again and again...).

I'd replace the carbonized coil. I'm betting that plug was loose and that the carbon is due to blow-by. Yes, if the engine was running OK before, there's actually a good chance you could clean it up and get it to work - but high-voltage is a funny thing, and it's a lot easier for voltage to go down a long carbon path than across a short air gap at the end of a spark plug. Even if it's only "missing a little", you'll very soon spend a lot more in extra gas than a new coil will cost.

If you haven't taken the plug out yet (hope not!) you can hit the area with compressed air first and blow the big chunks out, then I'd use engine cleaner / degreaser, or even brake cleaner and a lot of water to make sure there aren't any big particles of anything left in there. Then I'd either wait for it to dry out (expedited by sticking the corner of a shop rag down there), or better - blow it out with compressed air. Thing is, even with a good cleaning, it's likely that you'll end up with at least a little debris finding its way in there. With any luck, it'll just bounce around harmlessly and end up exiting the cylinder via the exhaust valve, and get burned to cinders in your catalytic converter. Do your best, but know that being perfect would involve a LOT of work. The good news is that you should have a pretty good sight line into that spark plug well to see how clean / dry it is down there before you put in the new plug.
 

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1.- Coil wont be affected by the oil.
2.- Oil can drip into the combustion chamber it will get burned

1.- You can re-use the coil
2.- I would not want dirt inside my combustion chamber... Use a shop vac and suck most of it, Do not allow it to fall into the combustion chamber.

You have to fix the oil leak.. Replace all valve cover spark plug O-Rings!!!!!
 

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Oil on the coil means the gaskets in the valve cover are leaking.

Like said above the coil with rust could be blow by and cause by a loose spark plug.

You don't have to do much of anything to clean the oil in the chamber, let it run into the engine when you remove that spark plug and it'll burn off.

I used brake clean to clean off the coils on mine that had oil in them. No issues at all just don't get it inside the coil.

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Discussion Starter · #5 ·
Thank everyone's quick reply. Here are 3 more pictures.

Yes that's right, I didn't touch those 2 plugs at the passenger side as I didn't know what might happen. So I decided to check with mdxers before proceeding with anything. Fair enough, since only 5 (or maybe 4) plugs are working, the CEL lighted up after I started the engine to move the car a little bit last night.

The dealer did the valve clearance adjustment at around 110K, which I assume the gasket should have been replaced. Although since that, the performance of car did downgrade a little bit from 20 MPG to 19MPG.

Will try some cleaning tonight to see how it goes. Will report back.

Again, appreciate eveyone's help!
 

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Discussion Starter · #6 ·
So I just explored the options on YourMechanic.com for the valve clearance adjustment. Sounds like it includes the replacement of all valve gaskets?

Is there any instruction on how to replace the spark plug O-Ring?

Thanks!
 

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I didn't have to replace any gaskets on my '04 with 170,000 or so miles, when I did my valves. Honda uses REALLY good gaskets, apparently. Of course, my engine wasn't leaking oil on my spark plugs, either, so I'd suggest ordering at least the valve cover gaskets when you get ready to do yours.

No idea about spark plug O-rings though... must be inside the coils?
 

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I didn't have to replace any gaskets on my '04 with 170,000 or so miles, when I did my valves. Honda uses REALLY good gaskets, apparently. Of course, my engine wasn't leaking oil on my spark plugs, either, so I'd suggest ordering at least the valve cover gaskets when you get ready to do yours.

No idea about spark plug O-rings though... must be inside the coils?
They are on the inside of the valve covers the coils sit between the gasket.

Also I'd be really surprised if your gaskets haven't been changed with that much mileage. The heat from the engine makes them brittle and they are rubber they'll get hard crack and boom oil goes right past them.
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Maybe the covers had been off, but the PO didn't recall having the valves adjusted (and he was a bona fide "car guy" who would have remembered), and there wasn't any receipt for any work on that part of the engine. OTOH, I suspect that the lack of cold weather here in the Phoenix, Arizona east valley helps keep the rubber bits happy (if not the clear coat). ;-)

I looked back through my photos and see those O-rings now (on the underside of the valve covers). They were in good shape, too. I knew I was taking a chance tearing down the engine to do the valves without a gasket set in hand, but in the end, they were all just fine. OTOH, we have spare vehicles, so I could have parked the MDX for a day or two while I got the gaskets. If that's not the case it's a good idea to have the gaskets in hand when starting that job.
 

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Maybe the covers had been off, but the PO didn't recall having the valves adjusted (and he was a bona fide "car guy" who would have remembered), and there wasn't any receipt for any work on that part of the engine. OTOH, I suspect that the lack of cold weather here in the Phoenix, Arizona east valley helps keep the rubber bits happy (if not the clear coat). ;-)

I looked back through my photos and see those O-rings now (on the underside of the valve covers). They were in good shape, too. I knew I was taking a chance tearing down the engine to do the valves without a gasket set in hand, but in the end, they were all just fine. OTOH, we have spare vehicles, so I could have parked the MDX for a day or two while I got the gaskets. If that's not the case it's a good idea to have the gaskets in hand when starting that job.
Ah didn't see you were in AZ. That's good luck. I ended up parking mine over night waiting for a gasket set. No big deal we have 4 vehicles and my motor cycle.

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Discussion Starter · #11 ·
So where is the valve cover spark plug o-ring? Is it the #2 in the part diagram? I thought it's part of the coil according to the diagram?

If not, would it be possible to post a picture?

Yes, I'm also in Phoenix :smile2:
 

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So where is the valve cover spark plug o-ring? Is it the #2 in the part diagram? I thought it's part of the coil according to the diagram?

If not, would it be possible to post a picture?

Yes, I'm also in Phoenix :smile2:
It's part of the valve cover gasket set. They are called spark plug tube seals.


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Here's a photo of one of my valve covers, showing the location of the spark plug O-rings. It's not shiny bright under there, but hey - for 170,000 miles, that's pretty impressive (the PO also used synthetic oil).



 

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Discussion Starter · #15 ·
Here's a photo of one of my valve covers, showing the location of the spark plug O-rings. It's not shiny bright under there, but hey - for 170,000 miles, that's pretty impressive (the PO also used synthetic oil).
Very helpful! Let's see what I will have tomorrow.......
 

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Ouch Habbyguy.. I think you must change your oil more often..
This is my TL-S engine with 194,000 Miles:

Front Bank


Rear Bank with common heat stain
 

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Hey, I didn't get the car until it had 160,000 miles on it (and those photos were somewhere around 170,000 miles). Even so, I don't get my knickers in a twist over the amount of build-up I saw. And yeah, I did clean up the valve covers before putting them back on, FWIW.

And if heat makes it worse, I have the best excuse in the world (living in Arizona). ;-)
 

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Yeah those heat stains on the rear bank are pretty common on all J-Series regardless of weather.. I have 120°F summers in here too and the front bank wont get stained over that.

My TL-S was dealership owned so that is how a properly maintained J-Series should look like inside. I am crossing fingers my MDX is clean inside since it was bought used. I will buy a can of Seafoam before my next oil change to help it out a little bit BUT I think the oil is what makes all the difference.
 

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Discussion Starter · #19 ·
Now, I had the valve clearance adjustment done, and got the mechanic to work on those 2 spark plugs. Apparently, he didn't do anything special to clean anything. Just took out old plugs and put in the new plugs. He didn't use the torque wrench when tightening the plugs. When doing the valve clearance adjustment, he didn't use any measurement either. I asked, and he said he had done this over 2000 times. So he knew it's good.

Anyway, now I got the mis-fire code. Even after I erased the codes, the CEL got off. The codes will come back after roughly 1 day's driving, and the CEL will get on again. The code I got are P0300, P0302, P0303, P0304, P0305, P0306. At the mean time, I feel the MPG is actually better, but the car does shake obviously at idle.

I ordered a new coil to replace the "burned" one, and will remove all coils, re-torque all plugs, and re-plug all coils to make sure the connection are tight.

Regarding the torque of plug, Acura service manual says 13 lb-ft while NGK website says 18 lb-ft. Which one is correct?

Anything else I can do to eliminate CEL/Mis-fire code?

Thanks for help! As always......
 

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""When doing the valve clearance adjustment, he didn't use any measurement either. I asked, and he said he had done this over 2000 times. So he knew it's good.""

TOTAL BS.... You cannot eye ball 0.28mm gap, and in any case that is totally un-professional. There is a gap measurement for a reason.
 
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