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Discussion Starter #1
Hello, have never posted here, although I've gleaned a lot of very helpful knowledge here over the past couple of years.

I own a 2005 MDX base model, 150,000 miles.

I've avoided scheduled maintenance, as have probably the last owners.
so not a lot of maintenance history available, I hate to say.

Anyway, I had a check engine light come on, blinking sometimes, and sometimes solid when first driving, and shortly after, the VTM-4 light would come on.

I ran the diagnostic codes, and got like 30 codes (many of them duplicates).

P0404 EGR Exhaust Gas Recirculation Circuit Range/Performance

random misfire:
P0300

single misfires:
P0301 (valve 1)
P0302 (Valve 2, etc..)
P0303
P0304
P0305
P0306

So, I decided to wing it...of course that didn't work.
I bought an EGR valve and replaced it with about 50% confidence, and 0% ease... the back nut on the egr was a piece of ****, but I finally replaced it.

Upon turning the engine, it was really noisy, and I located the hissing/squealing as coming from valve #6.
I removed the ignition coil, and low and behold, almost half of it was completely burnt off ( as pictured )
I then felt down in the spark plug tube to find the rest of it, but it was completely gone. i could feel the end of the spark plug though, and it was loose and free from the threads.
I removed it with a magnet.

The spark plug was closed at the end, I don't know what caused this.

So, upon trying to install a new spark plug in #6, I find that the threading is possibly damaged / melted as was some of the threading on the original spark plug.

Don't really know if anyone might have any advice, but I thought I'd post this to at least provide some info on what I've experienced with this car.

I guess I'm looking at maybe trying to re-thread the housing or even replace the head completely, but still wondering what other options I may have, if any.

Thanks for all the info I've already received here :)

not sure how to post img, but here's links of my asteroid coil head and spark plug:


 

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I'm not sure what the connection between the EGR job and the plug would be - maybe just a coincidence?

It's clear that the plug was entirely out of the head to melt the coil pack like that. I suspect it's been coming out for a while, based on what appears to be rust on the threads of the plug (hard to say - the photo is hopelessly blurry). I suppose it's always possible that you would be able to get a new plug to screw in, though it's a near certainty that the last couple threads on the head are going to be munged up, making it difficult to get started. If you're not successful, at the least you'll have to take the head off to have the hole re-tapped (if you're lucky and there's not a lot of messed up material), or an insert put in. You can't do this with the head on the car since it'll rain all sorts of metal shavings into the cylinder. I guess if it was my car, I'd probably try to get a tap in there to clean up the top threads (since the first few threads on a tap are a little smaller than the plug's threads), but I'd be VERY careful not to get any metal shavings in the cylinder - I'd grease the tap's threads, and then do a turn or two and pull out the tap, and clean it up. Rinse and repeat. Maybe use a shop vac in between tap insertions. Might work...

I'm betting your misfires were due to the valves badly needing adjustment. Over 100k miles, that's pretty much a certainty.

Good luck - you're gonna need it! ;-)
 

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I would also say Valve adjustment. Since you changed the EGR that's all that is left.

If you can do it (and have lots of time) go for it, otherwise get ready for $300.
 

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Discussion Starter #4
Thank you both for your advice, and sorry about the blurry photo.
Yes, I think re-tapping the threads is definitely the next planned step, so at least I know
it's sometimes do-able.
I did wonder if there might already be an insert in there, but I doubt it. Although, it does seem strange for the plug to back out like that.
Probably wouldn't try to do a valve adjustment myself, but $300 doesn't sound bad to save the vehicle.

Thanks again!
 

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Forbin where do you get valve adjustment for 300? The Honda and Acura dealers here start at more than that before tax.
 

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Nick, I've heard of this happening to other MDXs. I can only guess that it's because a plug wasn't tightened properly (and that can happen to anyone). I really hope you'll be able to get a new plug in there without TOO much effort. IF you're really lucky, the new plug - or tap - will clean up the threads without depositing too much debris into the cylinder. I suppose there HAS to be a mechanic's trick for extracting small amounts of shavings - maybe a piece of yard coated with something sticky fed in through the spark plug hole?
 

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Nick, I've heard of this happening to other MDXs. I can only guess that it's because a plug wasn't tightened properly (and that can happen to anyone). I really hope you'll be able to get a new plug in there without TOO much effort. IF you're really lucky, the new plug - or tap - will clean up the threads without depositing too much debris into the cylinder. I suppose there HAS to be a mechanic's trick for extracting small amounts of shavings - maybe a piece of yard coated with something sticky fed in through the spark plug hole?

Before using a tap, etc.:

Set the bad cylinder to TDC on the compression stroke. Both valves will be closed, piston at top.

When you are through, blow compressed air down the plug hole through 1/4" I.D. rubber or plastic tubing. Protect your eyes. repeat until nothing more comes out of the hole.
 

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Rethreading is possible, but not for many diy'rs. It is possible to make things worse. Here's a great video of a pro. It might be worth investigating a local source w/ experience.


Suggest running a thread chaser (not a plug) before attempting to install a new plug.

This problem seems to rarely happen to many engines suggesting human error as prime culprit.

good luck
 

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Discussion Starter #10
Huh, just had to type "keep America beautiful" in order to access this account.
Really? What kind of asinine **** is that?
Well, I was able to enlist the help of a seasoned professional to address the stripped spark plug housing.
I tried a thread chaser, but it just stripped out the aluminum threads even worse.
He did a heli-coil repair, and so far it seems to be working.
Just day 2, so who knows, but I was happy to hear the engine run without
anything making a racket inside the head.
I can only presume everything that burnt off the ignition coil just disintegrated enough to pass through the valve chamber.
I am not a mechanic, so forgive me for any loose terminology.

Did attempt to address a separate issue as well..
Have had many instances of battery going dead, but always chalked it up to leaving dome lights on.

Well, although that may be the case in some instances, there have been many times that my battery just seems to drain for no apparent reason. I kept running across reports of people having problems with the HFL / Bluetooth Module in these cars. I had a hard time finding anything related to a 2005 MDX, but seems it may be an issue, so I disconnected mine today. The phone feature didn't work when I bought the car, so when I read about battery drainage issues, seemed to make sense that mine might be causing problems. Was located above the map light, as suspected.

Well, fingers crossed until the next time :)
 
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