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2013 NAV here as well. Bought the car with 40,000 on it and was curious about all the soot on the bumper after a few months, so I started researching and learned some things about these particular GDI builds. They reposition the fuel injectors below the intake valve so the valves never get washed and build up carbon, but makes the EPA happy about efficiency and pollution. They also tend to run rich if they're idling. Blow by is intense with the GDI engines and the carbon will build up around the piston rings, apparently as early as 40,000 or less, if it was driven by a grandma (like mine before me). Just based off of what I have read about carbon build up the cat could've received a meteor of burning carbon that potentially was already plugged with hot carbon which lead to catastrophic failure of the engine unfortunately, in your case.

Intake valves are a known source of failure with GDI because of Carbon. I'm guessing the combination of the valves being on shaky ground and the meteors that inevitably caused failure to the cat had a terrible combo effect.

When my exhaust was replaced the mechanic told me the resonator was completely clogged and I knew exactly why. Heat and pressure from stomping on the accelerator will help clear this out a little I hear. I try to floor it every day as I round the corner to go home from work. I also use BG products for preventative maintenance. I know it's too late for you, but maybe others will take note.

TL;DR: I think Carbon build up caused this even though you had no warning. These engines seem to produce a lot of it.
I try to use "pure" gas (ethanol free) as much as possible. It produces much less carbon emissions than fuel with ethanol. GDI+ETHANOL =CARBON....
 

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I try to use "pure" gas (ethanol free) as much as possible. It produces much less carbon emissions than fuel with ethanol. GDI+ETHANOL =CARBON....
I don't know too much about ethanol, but what you're saying makes sense to me. Where do you go for pure gas?
 

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Sometimes the fuel offered as ethanol free also is not "top tier" gasoline. It's really hard to find ethanol free that is top tier.
Noted, Im currently running a tune that requires premium so that might not be an option for me.
 

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Sometimes the fuel offered as ethanol free also is not "top tier" gasoline. It's really hard to find ethanol free that is top tier.
There is a remedy for this too and yeah I may go a bit too far with redundancy but installing a 10 micron fuel filter between your low pressure fuel pump and high pressure fuel pump will give you piece of mind in whatever fuel you use.
I'd read where a GTA Time Attack car was having issues with fuel starvation on their turbo'd Subaru. They got second place but would've got 1st if they'd have that 10 micron filter setup on their car. This was their realization after finding out that sediment from their fuel tank was clogging their injectors under wot and high boost.
To me this was what I needed to hear to install my filter once I upgrade to the larger fuel line.

Long post sorry. ??
 

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I have the 2014 NAV with the manual standard 6 speed trans. The intake valves and injector tips were pretty full of carbon/oil build up at 16500 miles. I had the induction service done where they use walnut shells at the dealership. This fixed it and it ran great. I added an oil catch can to stop the PCV from dumping the oil vapor on to the intake. These engines DO NOT have a separate injector to wash off the oil from the intake as other GDI engines do! So far I get about 2-3 ounces of nasty vapor oil every 1000 miles in the can. In my opinion this is the gunk that eventually gets down into the catalytic. Imagine the oil build up AND the clogging fuel build up from the fuel injectors not particularizing the injector spray properly ,this causes misfires. Its a perfect storm that kills your catalytic. Get the full induction service done then add a good catch can is my recommendation for those that are having issues like lack of power, hesitation, carbon build up on exahaust tips, etc. Hyundai is reluctant to tell you about their design flaw! I also did a 91 octane tune that helped tremendously! Believe it or not, the factory ECU settings are a joke.
 

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Discussion Starter #29 (Edited)
Back for round two! Catalytic converter failed again just a little over 1 month out of the 12mo/12,000 mile engine warranty. CAT should still be covered under emissions warranty but the engine has a ticking sound again. I think it spun a bearing due to backpressure again. New short block has 9000 miles on it.

Update: Just heard back for the dealership. Cat is plugged. Why? no one seems to know. It's just one of those mysteries never to be solved until someone has this happen in a busy 8 lane highway and it causes an accident. They replaced the cat and said everything was fine. The mysterious new engine tick is clearly just a figment of my overactive imagination. Waiting to hear from Hyundai customer care. Two failed Cats one (if not both) causing engine damage needs to be looked into and what's causing it. I have my own theory but I'll wait to see what they come up with.
 

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Discussion Starter #30
Update:
Got the car back today. New catalytic converter installed. Service adviser says "tech didn't hear any ticking in the engine". I pick it up at the dealership drive it maybe 10 miles, roll down the windows at a stop sign and hear a very noticeable ticking sound.

I got a call from Hyundai customer care informing me that the engine is out of warranty and that I'll have to pay for any diagnostics BUT they "can" reimburse me for the diagnostic costs but can't guarantee if an issue is found that they'll cover any of the cost for repair. I told the person at Hyundai that this is the second failure of a catalytic converter on this car. I explained to them that nothing was done to figure out what caused the first one to burn down or the second. I told them they need to get someone involved to figure out why this car is burning up catalytic converters and then figure out what we'll do about the engine knock that is present as a result of the most recent failure. We'll see where this goes.
 

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Keep fighting dude!
 

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Update:
Got the car back today. New catalytic converter installed. Service adviser says "tech didn't hear any ticking in the engine". I pick it up at the dealership drive it maybe 10 miles, roll down the windows at a stop sign and hear a very noticeable ticking sound.

I got a call from Hyundai customer care informing me that the engine is out of warranty and that I'll have to pay for any diagnostics BUT they "can" reimburse me for the diagnostic costs but can't guarantee if an issue is found that they'll cover any of the cost for repair. I told the person at Hyundai that this is the second failure of a catalytic converter on this car. I explained to them that nothing was done to figure out what caused the first one to burn down or the second. I told them they need to get someone involved to figure out why this car is burning up catalytic converters and then figure out what we'll do about the engine knock that is present as a result of the most recent failure. We'll see where this goes.
Unfortunately I lost my 2014 modified NAV to a flash flood here in my city but think I can give you some insight on what may be going on with yours. The question is why does the cat keep melting? From my understanding the only way it melts and clogs your exhaust is when too much unburnt gas/oil carbon deposits accumulate in the tiny honey comb holes that run from front to back of cat. Now why is your car spitting that crap up? Your car has oil sludge build up along the intake valves due to PCV problems GDI engines have (read up on that on youtube). Chunks of that end up in your combustion chamber then out the exhaust to your cat. Also your in cylinder fuel injector tips are clogged causing the fuel spray to not particularize properly , this causes your exhaust to be rich in un-burnt fuel and chunks of oil that feeds the deterioration of your cat. It melts and clogs. What you need to have done is walnut blast the intake/cylinders. It's called an induction service. Also clean the injectors, replace the spark plugs and install an oil catch can with baffles (check youtube for the oil catch can info). It will run great after that for a long time. Hopefully you haven't already damaged the engine due to the back pressure if it got that bad.

:)
 

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Discussion Starter #33
Oh yeah, I'm definitely gonna keep up the fight.

The thing that gets me about this issue is each time this has happened there haven't been any codes set to make the CEL illuminate. My thinking is that when the cat plugs up, the downstream O2 sensor should read extremely lean due to no exhaust gas passing through the cat. This in turn should cause the emissions system sensors to set a code and the CEL should illuminate. This or the upstream should read extremely rich setting a code. No one that I've talked to has been able to explain why the O2 sensors aren't setting a code in the car when the cat fails. The issue seems to be the cat experiencing a catastrophic failure all at once rather than a buildup over time. If it was a buildup over time, I should definitely be getting some sort of emission code.

The next issue I'll try to resolve is the engine ticking sound that is now present due to high backpressure when the cat failed.

I'll keep folks posted as I learn more. I'm trying to get Hyundai to address the issue of the cat failure since there has to be some sort of issue in tuning that is causing this car to burn through cats.
 

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The ticking from the high pressure fuel pump could be what you are hearing.
 

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Discussion Starter #35
The ticking from the high pressure fuel pump could be what you are hearing.
I don't think it is. This engine was very quiet prior to the cat going again. Also, the sound oddly goes away between shifts. It's very noticeable at a stop sign. I'm familiar with the sound of a HPFP as well as lifter tick and piston slap (owned a Suby) This has a different sound that seems to come from the passenger side down low.
 

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Discussion Starter #36
Results came back from the oil analysis
Iron 100 ppm universal average 7 ppm
Aluminum 90 ppm universal average 3 ppm
 

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Results came back from the oil analysis
Iron 100 ppm universal average 7 ppm
Aluminum 90 ppm universal average 3 ppm
That does not have much significance without a baseline set from previous analysis reports.
Probably of more importance would be:
1. The distance between oil changes.
2. The acid index of the tested oil.
3. The viscosity of the tested oil.
4. The amount of water contamination.
 

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Results came back from the oil analysis
Iron 100 ppm universal average 7 ppm
Aluminum 90 ppm universal average 3 ppm
I don't understand your post. What is the Iron ppm, 100 or 7? Same for the Aluminum, was it 90 or 3?

I believe the normal range for iron is in the 100-300 ppm range and aluminum is something like 10-30 ppm.

Can you post a pic of the sheet? Usually the highlight in red if something is off or out of range.
 

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Discussion Starter #40
That does not have much significance without a baseline set from previous analysis reports.
Probably of more importance would be:
1. The distance between oil changes.
2. The acid index of the tested oil.
3. The viscosity of the tested oil.
4. The amount of water contamination.
1500 miles on that oil sample. No water, No fuel. The Iron, Aluminum, Chromium and Silicone were all considerably out of spec. I had to reason to do oil samples prior to this because the short block only has 9000 miles on it and showed no issues until the cat plugged up again.

I would think that Aluminum being 22x the average and Iron being (corrected averages for 1.6L Gamma was 16 ppm) 6x the average would be significant regardless of baseline from a previous test unless my Aluminum and Iron were higher in those tests and somehow are now coming down.

Long and short, there's something wrong internally when you have the elevated Iron, Aluminum and Chromium (not included previously but sample was 4 ppm and average is zero)
 
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