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Discussion Starter #1
03 MDX 151K.
Well maintained, transmission oil I changed few months back (Honda).
I was driving today around 70MPH and all of a sudden engine check light came on and kept blinking.
I slowed down and felt vibrations.
I also was smelling burnt oil.
I slowed down, pulled over restarted car and it was rough.
I was able to drive home another 10 miles.
Now VTM and check engine lights are on.
I checked transmission oil and it looks OK.
I will check code later today.
Few months back I was hearing whistle/whine sound around 65-75 MPH.
I have a feeling damage to transmission.

Any suggestions on checking before taking to garage?
When car is parked and I start the engine the engine has vibrations (as if engine mount is broken).
I did change 2 mounts earlier this year (front and side), didn't do back one.
I hate to give up on this car if I can save it, at least for my kids.
 

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Your description leads me to suspect that at least one cylinder isn't firing... It may not be related to the transmission, at all.

First step would be to find out what DTCs were thrown. Do you have access to a code reader?
 

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Discussion Starter #3
Thank you.

Your description leads me to suspect that at least one cylinder isn't firing... It may not be related to the transmission, at all.

First step would be to find out what DTCs were thrown. Do you have access to a code reader?
Your description leads me to suspect that at least one cylinder isn't firing... It may not be related to the transmission, at all.

First step would be to find out what DTCs were thrown. Do you have access to a code reader?
Wow! You were right. This forum is my lifeline for the MDX :)

I got multiple cylinders misfire P0301-P0306.
I cleared the codes and check light and VTM light went off.
Took it for a drive and engine check light came back after a mile or so.

One thing I did not mention was I drove through heavy rain (like 2 hrs) when original problem happened.
Tomorrow I will reset code again, dry out spark plug coils etc.

This gives me better feeling because even when car was driving little rough on a test drive, all the warning lights went off for a mile or so.

Again thanks for pointing me right!
Happy Thanksgiving to all!
Robert
 

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Discussion Starter #5
Already done.

Sounds like it might need a valve adjustment to me if it hasn't had it done because those are the exact symptoms.

Hi, Valves were adjusted 2 years back at Honda service, because I was getting VTM4 light.
That took care of VTM4 issues.
 

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Discussion Starter #6
Since my car has 151K I am going to change ignition coils.
Given that I put in new spark plugs 3 years back and valves were adjusted by Honda about 2 years ago.
For a pack of 6 coils for $79 from Amazon is a good first crack at this.
2 years ago I had also opened the upper cover and checked EGR ports, it was clean.
I will check spark plugs today for any indications...

Any other suggestions?

PS: How do I change title of this tread? It's not really transmission problem.
May be 'engine misfire that feels like transmission going?' :)
 

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All 6 coils going out at same time is unlikely. Aftermarket coils may be poorer quality than originals. Suggest some diagnostics to confirm problem. Looking at misfire counter w/ advance scanner can ID a particular cylinder as primary fault.

More likely a lean or rich misfire due to air/fuel delivery fault. Any change to Long Term Fuel Trim (LTFT), either > or < 10% might suggest this to be the case.

good luck
 

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Discussion Starter #8
Thanks I used my scanner and it repeatedly says P0304 -Cylinder 4 misfire.
So I will try to change coil on that one first.
I believe the order of cylinders is.

--- fire wall ---
1 2 3
4 5 6
--- Radiator ---

I also checked Long Term Fuel Trim and it stays steady 0.0 %.
I recorded 49 frames all the same %.
Don't know how to dump to computer yet.
Only 1 DTC comes up P0304

Thanks,
Robert
 

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EDIT: Never mind you are correct.

Possibly torque converter?
 

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The coil packs build up a rust colored deposit on the stick portion of the coils over time. That can cause misfires when wet. Pull all your coil packs, blow out any water in the spark plug wells, and clean the coil sticks with soap and water, then electrical contact cleaner. After cleaning, inspect the whole coil pack for any sign of plastic cracking. That can allow water to short the coil internally.
 

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Discussion Starter #11
Total melt-down

I opened thee 4-5-6 spark plugs.
#4 was totally burnt (see pictures).
5-6 were fine.

When I pulled out #4 the coil came out as you see in the pictures.
Then I used magnetic tool and the plug just came out.
I guess melt down made it just come off?

I hope there is no damage to threads in the engine block.
I did try to put a spark-plug from #5 in to #4 and it did threaded in...

Waiting for coil set to arrive tomorrow to try new plug in #4 and change front 3 coils.

I wonder what happened to the rest of thee coil (probably just burned up?

Any suggestion before I try things tomorrow?

Also what could have caused this kind of melt-down?
Clearly there was a fire there.
BTW: I was the one who changed spark plugs few years back. I had not noticed any noise or issues with the car till recently.

Thanks,
Robert
 

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The electrode fall off the spark plug? then the arc was made in the body of the spark plug which is not very hard causing it to overheat and melt.. Clearly this was a spark plug failure if the electrode did fall off inside the combustion chamber.
 

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Discussion Starter #13
The electrode fall off the spark plug? then the arc was made in the body of the spark plug which is not very hard causing it to overheat and melt.. Clearly this was a spark plug failure if the electrode did fall off inside the combustion chamber.
Yes it must have fallen inside.
Is it worth fishing for it using my magnetic snake?

BTW: These were Honda plugs I bought.

I still don't know is what caused this?
 

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Yes it must have fallen inside.
Is it worth fishing for it using my magnetic snake?
If it fell into the combustion chamber while you were trying to remove the plug, then yes, I'd get all the bits out before you start the engine, again.

If it fell in and the engine was then started, you may have damage to the piston, cylinder walls, head, or valves. I would use a borescope or inspection camera to inspect the combustion chamber. I'd also perform a compression check.
 

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Discussion Starter #15
I don't think it fell off during my pulling the plug out as it just came off with my magnet, plug was just sitting there.
Whatever damage was done was already done while I drove it back home.
Whatever caused the spark plug to explode took off the tip.
If you see the coil damage picture fire went up the coil...

BTW: I have small amount of oil on coil at cylinder 5.
 

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These Honda engines are notorious for spark plugs coming loose, especially in the middle cylinders. Dunno why. Once the plug gets loose, bad things start happening. Overheating, arcing where they shouldn't, blow-by combustion gases torching coils, yada yada yada.

If the spark plugs aren't tightened to the correct torque, they are more likely to come loose. ( But sometimes factory tightened plugs come loose ).

BTW, Honda/Acura doesn't make spark plugs, they use ones made by Denso and NGK. But it might be prudent to double-check the part numbers on the plugs. It would be unfortunate if someone sold you the wrong spark plugs.
 

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Discussion Starter #17
That's probably what happened.
I installed plugs and may not have torqued right.
I did buy them from Honda service not necessarily it's Honda brand!
 

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FWIW, I did a valve adjustment a few months back for same codes and in doing so, found plugs #2 and #3 loose - only about 3/4 turn. One of the coils was miscolored so I suspected some blow by and hot gases coming through.

Re the your picture of the burnt plug, are the threads melted away or is there something in the threads? Asking because if there is material in the threads and it's metal instead of burnt oil or plastic from the coil, the metal could be from the threads in the head. Although you already tried another plug in #4, you might want to inspect that burnt plug.
 

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There are a number of posts aboiut #4 cylinder spark plug loosening and being ejected. How this occurs other than a plug left loose is unclear. If loose plugs were the root cause you would not expect #4 to be the culprit so frequently.

Looking at your pics damage to cylinder head threads seems highly likely. You may want to explore options for thread repairs. Check Scotty Kilmer's channel on youtube. There are many other examples. His is one of simplest DIY's I've viewed.

good luck
 

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Discussion Starter #20
Ok so I tried to put back a new spark plug and it just keeps turning.
I did put the coil on top to hold in place and did not connect the wire.

That throws cylinder 4 misfire.

Is this something mechanic can fix and tighten the sparkplug?
How big a job is that?

Thanks,
Rober
 
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