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2005 4x4 6MT
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Discussion Starter #1
Hi Everyone,

Learn from my mistake. Always replace all coils when one goes bad, it will haunt you, read on...

I had a misfire on the right bank due to a bad coil, which then ruined the right side primary cat, I replaced the coil and the cat (simple job but the clearances for tools makes it take a good bit of time).

Drove happy with no misfires or check engine lights for a few months until the other two right bank coils failed. The truck misfired again and the check engine light came on (420). I had just done the cat job so I really just wanted to live my life in ignorance, and drove it for several thousand miles.

Finally on the highway I lost all power, truck drove only about 5-10 mph and sounded knocky. In short I melted the right bank primary cat into the right bank secondary cat and clogged it.


Here is a video of the empty melted primary cat:

And the ceramic sand from the clogged secondary cat:

I replaced the right bank secondary cat (and ALL the coils), and now she runs good as new!

I would hate for anyone to repeat my mistake ever as coils are cheap and easy to replace, and please buy Hitachi/OEM. Please replace all your coils if one goes bad. SMH!
 

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Discussion Starter #3
Sorry for your troubles and thank you for sharing you’re experience!
Thanks XAZ! I just would hate for someone to repeat this mistake. Now I gotta replace that primary right cat again once the weather is warm since that "most likely" will not pass emissions. Not the worst job, but its a pain due to the working room on those upper cat bolts.
 

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I had this happen to me, I couldn’t figure it out at first though because there wasn’t a smell. But I just died out with a knock sensor code and misfiring
 

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This happened to me. Thought the SMOD bypass konked transmission because I lost all power on hills. Don't ignore misfire codes on rear cylinders, could have saved stranding in a small town. Mechanic dinged me for $1000 (I approved all coils not knowing the marked up price for each) and I still had to buy cats since his shop didn't mess with exhaust.
 

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Discussion Starter #6
Ouch, it pains me greatly to hear that this has happened to others.

I hate the lost time and the lost money. People work hard for the money, and time is something we cannot replace.

If I could grab a megaphone/sponsor an infomercial and tell random folks on the street/TV to change the coils preemptively before failure I would!!!
 

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I would also tell people not to lend out there Xterra out also.
I did and it cost me a clutch and flywheel .


Sent from my iPhone using Tapatalk
 

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Thanks for posting this information. I'm a believer in replacing parts before they fail and playing the averages on part lifetimes.

At what mileage and age did the first coil fail?
 

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Discussion Starter #9
Thanks for posting this information. I'm a believer in replacing parts before they fail and playing the averages on part lifetimes.

At what mileage and age did the first coil fail?
Agreed! I will break it out by cylinder number in chronological order as I have a theory that the intake plenum sitting above the right bank 'cooks' the coils on that right bank, particularly the number one cylinder.

Cylinder One: ~80k miles per service history (previous owner replaced that coil and primary right bank cat at that time, I could tell because I got the service records and the cat and o2 sensor were clearly less rusty than the left bank, replaced with OEM coil from Nissan per coil part number found).

Cylinder Five: ~185k miles (replaced and ruined right primary cat the first time, technically the second time if you count previous owner's replacement of the right primary cat)

Cylinder Three: ~190k miles

Cylinder One: ~190k miles +1k miles about (melted right primary cat into secondary right cat, which led to the videos etc.)

Cylinder Two, Four, and Six: Replaced at 194k miles as a precaution to protect the left bank cats given what just happened.



So my theory: The number one cylinder coil sits under the intake plenum the most, and therefore cooks way quicker than the other coils on that right bank, and the right bank coils 'cook' because the intake plenum sits on top of them. The left bank coils do not ever really 'cook' because they are not under anything so they may stay at cooler temps and therefore not cook.

This confirms why everyone seems to get the 420 code, because they are cooking the right bank coils do to a poor design on the intake plenums routing over the right bank coils, specifically the number one cylinder coil.

Please accept my doctoral thesis for my PH.D. on Nissan intake plenum routing and its effect on right bank coils. (jokes)
 

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My X has 364,000 miles and all original coils. I have owned it since new. I could be just lucky but I honestly haven't heard of a lot of coil failures around here - although your correct a misfire will destroy a cat pretty quickly.

Were your coil failures marked by specific cylinder codes for misfire - ie P0301, or random misfire P0300, or something else?

First cat went at 240,00 miles - efficiency code only - replaced and it showed no evidence of implosion. The other side at just over 300K. Replaced both primaries at that time since the one replaced earlier was aftermarket and was throwing the occasional code. Both aftermarket cats have now been on for about 45k I think - no issues so far.
 

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Discussion Starter #11 (Edited)
My X has 364,000 miles and all original coils. I have owned it since new. I could be just lucky but I honestly haven't heard of a lot of coil failures around here - although your correct a misfire will destroy a cat pretty quickly.

Were your coil failures marked by specific cylinder codes for misfire - ie P0301, or random misfire P0300, or something else?

First cat went at 240,00 miles - efficiency code only - replaced and it showed no evidence of implosion. The other side at just over 300K. Replaced both primaries at that time since the one replaced earlier was aftermarket and was throwing the occasional code. Both aftermarket cats have now been on for about 45k I think - no issues so far.

Only ever got a p0300 for all of them, did the coil disconnect while running method to discover which coils were misfiring.

Quick question, does your right bank exhaust manifold have a heat shield from the factory? I noticed only my left bank has a heat shield over the exhaust manifold when doing the cats, that was my second theory but the truck came like that from the previous owner, could not tell if by design. Let me know, as that could be the cooker of coils right there!
 

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If i ever have to mess with or replace my exhaust again im thinking about nixing the secondary cats.

I had a coil go out on the passenger bank and shortly after that primary cat went out. I replaced the coil almost immediately after it went bad. I think that it let some fuel pass into the primary cat which caused it to burh out. I replaced the cat when its code went off, and the was fine for a while, then the primary o2 on that bank went out.

been fine since then. but yeah form this experience I will always make sure to take care of these issues as soon as the come up, as even running with them for a short period can lead to damaging other components or worse.
 

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If i ever have to mess with or replace my exhaust again im thinking about nixing the secondary cats.

I had a coil go out on the passenger bank and shortly after that primary cat went out. I replaced the coil almost immediately after it went bad. I think that it let some fuel pass into the primary cat which caused it to burh out. I replaced the cat when its code went off, and the was fine for a while, then the primary o2 on that bank went out.

been fine since then. but yeah form this experience I will always make sure to take care of these issues as soon as the come up, as even running with them for a short period can lead to damaging other components or worse.
I would also like to delete my secondary cats - but I have heard it makes it quite loud - there are a few threads on here. I am not really interested in making it louder so I am not sure what the answer to that is.
 

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Only ever got a p0300 for all of them, did the coil disconnect while running method to discover which coils were misfiring.

Quick question, does your right bank exhaust manifold have a heat shield from the factory? I noticed only my left bank has a heat shield over the exhaust manifold when doing the cats, that was my second theory but the truck came like that from the previous owner, could not tell if by design. Let me know, as that could be the cooker of coils right there!
Yes there are heat shields on both sides from the factory. Many guys remove them when changing the cats because they break all the bolts and don't want them ratting around in there, which is understandable. I was able to get most of my bolts out by taking the heat shield off when the engine was hot (then letting it cool before going further).

Having said that - I doubt your "cooking" your coils from any ambient condition. The heat in the coil pack comes from the direct conductivity of the spark plug == electrode == coil - which essentially gives you a highly conductive metal path directly from the combustion chamber directly inside the coil pack itself. I am sure its multiple times hotter in the coil itself than ambient temps anywhere under the hood.
 

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Discussion Starter #15
Yes there are heat shields on both sides from the factory. Many guys remove them when changing the cats because they break all the bolts and don't want them ratting around in there, which is understandable. I was able to get most of my bolts out by taking the heat shield off when the engine was hot (then letting it cool before going further).

Having said that - I doubt your "cooking" your coils from any ambient condition. The heat in the coil pack comes from the direct conductivity of the spark plug == electrode == coil - which essentially gives you a highly conductive metal path directly from the combustion chamber directly inside the coil pack itself. I am sure its multiple times hotter in the coil itself than ambient temps anywhere under the hood.
That would make sense, I just wish I knew why the right bank coils died. Specifically the number one cylinder. The other coils made it to about 190k miles which is great for coils imho. Besides these coils and the resulting cat issues, the truck never had big issues, and a bad coil really is not a big issue, just the working room for the cats makes it a pain of job to change them out should they get damaged by misfires.
 

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Discussion Starter #17
Can you tell if it is misfiring without a OBD reader? Like, does it make a sound to look our for?

I have a basic OBD reader, but I have been chasing different codes on this truck since Day 1. Its starting to be not fun.
Yes you can, start the truck and while its idling unplug each coils' connector one by one (do not remove the coil, of course you would need to remove the single bolt holding it down to do so, but do not please).

If you notice a change in engine rpms or roughness, that coil is good since unplugging its connection did have an effect, example: drop in rpm/rough running.

Do this coil by coil until you notice that one coil when its unplugged does not have any effect on the engine, which therefore means its bad since if it were good, unplugging it would have an effect on the engine.

This is common for testing a number of misfire situations. Hope this helps!
 

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Hi Everyone,

Learn from my mistake. Always replace all coils when one goes bad, it will haunt you, read on...

I had a misfire on the right bank due to a bad coil, which then ruined the right side primary cat, I replaced the coil and the cat (simple job but the clearances for tools makes it take a good bit of time).

Drove happy with no misfires or check engine lights for a few months until the other two right bank coils failed. The truck misfired again and the check engine light came on (420). I had just done the cat job so I really just wanted to live my life in ignorance, and drove it for several thousand miles.

Finally on the highway I lost all power, truck drove only about 5-10 mph and sounded knocky. In short I melted the right bank primary cat into the right bank secondary cat and clogged it.


Here is a video of the empty melted primary cat:

And the ceramic sand from the clogged secondary cat:

I replaced the right bank secondary cat (and ALL the coils), and now she runs good as new!

I would hate for anyone to repeat my mistake ever as coils are cheap and easy to replace, and please buy Hitachi/OEM. Please replace all your coils if one goes bad. SMH!
I had the same happen to my x. Being 100 miles from any cell service I limped along and proceeded to destroy my engine when the contents of the cat sucked into the engine and destroyed the rings. I spent a holiday weekend replacing the engine. 4 days and mucho dinero. Now I keep spare coils and a toolbox in my vehicle. Had i done this before I ruined my engine I would happily spent the money on suspension mods.
 

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I had the same happen to my x. Being 100 miles from any cell service I limped along and proceeded to destroy my engine when the contents of the cat sucked into the engine and destroyed the rings. I spent a holiday weekend replacing the engine. 4 days and mucho dinero. Now I keep spare coils and a toolbox in my vehicle. Had i done this before I ruined my engine I would happily spent the money on suspension mods.
I had the same happen to my x. Being 100 miles from any cell service I limped along and proceeded to destroy my engine when the contents of the cat sucked into the engine and destroyed the rings. I spent a holiday weekend replacing the engine. 4 days and mucho dinero. Now I keep spare coils and a toolbox in my vehicle. Had i done this before I ruined my engine I would happily spent the money on suspension mods.
132593
 

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Discussion Starter #20
Ouch man! I agree that having a spare coil is a good idea, given the risks of running on a bad one during even a minor road trip. I am so sorry that ceramic dust got into the pistons, that is my current fear. I changed the oil and oil filter about 200 miles after replacing the secondary cat, and it has been about ~750 miles since and the oil level is staying consistent, phew. When I drained the oil thankfully I did not see any grit, and the filter did not seem to have any grit either when I inspected. That sounds like a horror story, wish you had pics of the oil filter cut open, I would assume a lot of the grit got stuck in there.
 
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