They were using that excuse to make you pay for the new catalytic converter. They're wrong but they can do that. Back pressure doesn't keep it from getting clogged, that would make no sense.

So basically, before it got clogged it was running fine and after they replaced it, it started doing this?

 

There's been a couple of threads here about clogged cats. As far as I know both were replaced under warranty, and both were NAVs.

Did they do anything else besides replace the Cat? Reflash the ECU, or anything else?

 

It might have something to do with the fact that NAVs don't require anything over 87 octane.

Many people believe that the higher the octane the better quality (or how clean) of the fuel. Maybe you know what octane is for maybe you don't but I will tell you anyway.

More octane is added to fuel to increase the flash point of the fuel. The reason they would need to do this is for higher compression engines (higher compression equals more heat) and for forced air induction engines to prevent premature detonation of the fuel. Most of your average vehicles run best on 87 octane cause a higher octane has a flash point that is higher than what the car can handle.

Maybe since you were running 91 octane, less of the fuel was being burned and started clogging your catalytic converter. Also maybe (not sure why but still maybe) you are able to notice your engine running poorly now on the higher octane, again not sure why you would be able to notice now and not earlier.

I would try running 87 octane for a few tanks of gas and not putting in the fuel treatment.

 

Nothing wrong with taking it out every now and then and "blowing it out". Can't do no harm and it may help

to alleviate the problem in the future.

***

 

I know what you are talking about. Mine did the same thing. Mine just stalled out. They told me the cat was clogged, and they replaced it. When I got it back, it had a knocking sound, kind of like a diesel. So I brought it back the next day. As of right now, I am waiting for my new engine to come in for dealership to swap out. I have stock exhaust, and only 32K miles on my 2013.

When they gave me the car back the first time, they did say that they updated the ECU. Would the fact that we are stuck with gas with ethanol make matters any worse? I mean, there is nothing we can do about that. But would it be a contributing factor?

 

No. That's a standard type of gasoline across the country. The car can use ethanol mixtures just fine. You're talking like 10% to 15%, right? Not something like e85?

 

Correct. Just ethonal added fuel.

 

Haven't posted in a while. Still have my 2012 NAV. June w/79k miles on car code P0420 appears. Dealer replaced exhaust manifold, exhaust pipe & catalytic system assembly (cat & O2 sensors) under emissions warranty which runs out at 80k. Lucky for me. I have had the Turbo Kits CAI & ABE since 20k miles with no issues. Recently thru P0014 code and dealer found bad Oil Control Valve, replaced under engine warranty and on the road again. Trip to Maryland and CEL back on with same code @83k, Changed Camshaft Position Sensor as advised (sensors NOT covered under 10/yr/100k warranty). Reset ecm and on road again. Light on again P0014 code again & 85k miles on clock. Now dealer says both CVVT's need to be replaced (under engine warranty). TBC....

 

WELCOME BACK! Thanks for the update, I am at 81700 miles right now and haven't had any issues like you mentioned (fingers crossed!)

 

Similar scenario with me, I have a post elsewhere. 2012 NAV with just under 30k miles, injen intake, megan catback. Dealership said the cat came apart internally, replaced it under warranty. Now my car is making a strange loud ticking sound that wasn't there before, delayed start and the exhaust pops while idling. Guess I need to take it back.

 

I encountered significant engine knocking problems after implementing a heavy camming project on the cheap.
I later realised this is not the engine modification to do on the cheap so I invested heavily in getting it done properly.

Now my 1.6L powerplant has a heavy cam and no knocking.

Good plans bring good outcomes.