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Started getting the P300, P302, P3023...etc codes and took my MDX to the shop. I have dealt with this before and ended up replacing all my Ignition Coils and that worked for about 6 months.

Now the shop has my MDX and they adjusted the valves and checked everything out and still getting the codes coming back in various cylinders. I'm starting to worry because they really don't seem to know what's wrong. It's like they are just taking guesses.

They cleaned the Fuel inectors...and no help. Now they want to clean something related to the exhaust recirculation system thinking that could be the problem.

This is virtually a perfect MDX; well maintained with no major issues and now it seems like she's on life support.

Anybody have some advice I can throw these guys. I know they are good at what they do, but I'm getting worried.
 

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Sorry to hear this, I have a 2002 MDX and had to replace the EGR valve recently to eliminate a hesitation I felt while driving at 80Km/h but my check engine light didn't come on...my issue was due to accumulated carbon build up, I imagine if the valve failed completely that the CEL would illuminate and you might see the same codes.

Ask your dealer if that is what they want to try next (EGR valve replacement) as it is very easy to do yourself, the part is locted on the front of the manifold and costs about $200 so you can save yourself $100 in labour.

I should also mention that I used to take my car to the dealer to get all of my work done and to diagnose issues until I realized that they didn't know what they were talking about (they thought my hesitation problem was due to a failing computer and recommended I just drive it and if it got worse then they would replace the CPU...idiots)...if you have the time to research this site you will find it is better to do things yourself and the members here know more than most mechanics.
 

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Multiple misfire codes are rarely coil related, usually it's an EGR problem. First thing I always suggest in this instance is to write the codes down, swap the coils around from a cylinder that doesn't have an error to one that does, and see if the misfire codes change.
 

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Thank you both for your input. Thankfully they were able to get my MDX back on track again. What they ultimately ended up doing was adjusting the valves; cleaned the fuel injectors and clean the EGR passages. She's purring like a lion again and no more misfire codes. What the problem ultimately ended up being was the EGR passages. Even after they had adjusted the valves and cleaned the fuel injectors the codes were still coming on.

Thanks again for your help; it's always appreciated.
 

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Thank you both for your input. Thankfully they were able to get my MDX back on track again. What they ultimately ended up doing was adjusting the valves; cleaned the fuel injectors and clean the EGR passages. She's purring like a lion again and no more misfire codes. What the problem ultimately ended up being was the EGR passages. Even after they had adjusted the valves and cleaned the fuel injectors the codes were still coming on.

Thanks again for your help; it's always appreciated.
From my own personal experience and from what I've read, the valves needing adjustment is usually the biggest culprit in causing random misfires.
 

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From my own personal experience and from what I've read, the valves needing adjustment is usually the biggest culprit in causing random misfires.
Yes, I had read the same thing on a few of the other threads in this forum; that's why I had my mechanic start there. He indicated that a couple of the valves were "tight" and needed adjusting. Unfortunately even after they did that the codes kept coming back on. At that point they had to keep trying to figure it out. Thankfully they were able to do so before the bill went over $500.

Like I said, she's purring beautifully at this point and seem to be in good shape for the holidays.
 

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2004 mdx, multiple misfires CEL

I need help. CEL is on. My mechanic has so far tried the following.

new EGR valves, new catalytic convertor, new coils, new plugs.

what else could it be?

the car runs fine, no issue when driving. we have been tackling this issue since Christmas.

thanks
 

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I need help. CEL is on. My mechanic has so far tried the following.

new EGR valves, new catalytic convertor, new coils, new plugs.

what else could it be?

the car runs fine, no issue when driving. we have been tackling this issue since Christmas.

thanks
You did everything except the valve adjustments. That should have been the first thing to look at. Your mechanics really didn't know what he was doing. New catalytic converter for a misfire code? Really?
 

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valve adjustment and fuel injector cleaning on my 02 with 163k just fixed my misfire codes. independent service guy said the cylinders were "tight". car runs better, now need to address o2 sensor issue.
 

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First off thanks for all the help everyone has given me in troubleshooting my 06 MDX. Found it was a coil by un -plugging them. Take a look at mine. I almost puked when I saw this.
Oh dear!!

I suspect this is a result of a plug "backing out" We have all heard of the loose plugs, I am guessing this was the extreme. Have you carefully pulled all those pieces out yet? I imagine you are possibly looking at head replacement, or worse.

As a side note, about a month ago, I did the valve adjustment on mine. Also did the plugs and other various stuff the Previous Owner failed to perform. Anyway, I always use the widest allowable clearance setting for the exhaust valves in the book, but for some reason I'm speculating worn valve train, that setting introduced a tick, that I have been chasing for a few weeks now, but long story short, I have put a couple thousand miles on it, in between having the valve covers off four times now, and twice I rechecked my plug torque, and guess what!?!? Yup, upon rechecking them the first time, they were all loose to some degree, and #2, & #5 were the worst. Not sure what to make of that, but it is what I found.

I HIGHLY recommend when servicing plugs in any way on this engine, re-torque them after a few hundred miles.
 

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Working on removing the pieces. Not a easy task. Dental tools, vacuum, etc. Got all but one piece out and I do believe it has welded itself to the remaining plug body. Going to finish getting it out over the weekend. I'll keep u all up dated. Ordering all new coils and plugs from Rock auto. Half the price of local auto stores.
 

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Thank you both for your input. Thankfully they were able to get my MDX back on track again. What they ultimately ended up doing was adjusting the valves; cleaned the fuel injectors and clean the EGR passages. She's purring like a lion again and no more misfire codes. What the problem ultimately ended up being was the EGR passages. Even after they had adjusted the valves and cleaned the fuel injectors the codes were still coming on.

Thanks again for your help; it's always appreciated.
I cleaned the EGR port & passages a few days ago after I got multiple Misfire codes on all cylinders. So far so good, CEL doesn't come back and the mileage improves 1 to 2 mpg. There were oil in the ports! It should be cleaned every 1 or 2 years. The last time I cleaned it was 2 years ago.:)
 

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Hey guys. I started having this issue yesterday on my way to the beach. I’m 200 miles from home, check engine light is flashing (checked codes at oreilly’s to confirm multiple misfire issue), AND my VTM-4 light has come on (without me pressing the VTM-4 button). So, I’m wondering if it’s safe to drive this vehicle home where I can work on it, or if I need to get it worked on locally before I head home?
 

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No guarantees but if it’s missing only on start or cold, you’re probably OK. If it’s missing during regular or highway driving, would avoid driving it.

You didn’t say what year and miles or maint history.

One quick thing you can do is check for loose spark plugs. You’ll need an Allen wrench to remove the coils and spark plug socket, extension, and wrench. OReilly has loaner tools.

Good luck!
 

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It's a 2006 with 238k miles. I've had it the last 113k or so and haven't replaced plugs, coil packs, or any of that. I can order a full set of coil packs a lot cheaper online than buying them individually from O'Reilly, so I was hoping to wait until I get home. Codes say four cylinders are misfiring.

What I have replaced are the timing belt and water pump (recent), alternator (also recent), radiator, and some other things with the suspension system.

Guy at O'Reilly said the battery was ok but also indicating charge needed. Alternator was reading ok. We checked the battery, which is only about a year old, because it's also kinda struggling about to crank. He said if the battery is not giving enough cranking amps, it can cause the electrical system to act 'strange' after it starts running, which could also be causing it to misfire. This sounded odd to me, but thought I would mention it here to see if anyone agrees with that theory. Maybe I just need to replace the battery?
 

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Oh, and the CEL flashing and VTM-4 light didn't happen until I was almost to my destination Friday night, so I assume it's misfiring while I'm driving.
 
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