Blown engine ruins catalytic converter?

[2010Civic]

I bought a 2008 Honda Civic with a blown engine. The previous owner hit something on the highway which destroyed the bottom of the radiator. They kept driving until the engine fried.

I have replaced the engine and the car runs great. After driving it I got a P0420 code for catalyst system deficiency below threshold. I tried a new secondary o2 sensor from my 2010 (which is in perfect running order) and the light came back. So it is looking like the catalytic converter is bad.

I wonder why the cat went bad? The engine didn't ingest oil and I assume it didn't ingest coolant into the cat. Seems odd it would go bad.

Is there anything else I should check before getting a new cat?

Thanks

 

[GSCJR]

Could it have been a preexisting condition?

 

[ARCOgraphite]

Drive it med - hard on highway and wring and clean THAT THING OUT. 1/2 to WOT at 4000-5000 rpms for 15 mins. MAYBE IT WILL RESPOND.

ARE YOU SURE ALL THE INTAKE, EGR AND VACUUM PLUMBING ARE CORRECT? Don't disco the egr motor, that will cause engine to pull timing due to ping/knock and affect the ex mixture.

 

[supton]

Wonder if the cat ran hot and melted / took internal damage. I'd think it'd toss a code pretty quick, but maybe it finally (quickly) reached its limit.

 

[901Memphis]

Try a few tanks of shell premium... Seriously. Helped with a co workers 2007 Accord with same code. He stopped using shell and it came back and when he switches back again it goes away.

I'm guessing they have a sensitive threshold for cat efficiency more than American cars

 

[Chris142]

Prolly pre-existing.

 

[2010Civic]

Yeah, it could have been a problem before the engine blew. I'd guess it wasn't but who knows. Has anyone tried cleaning the cat? I was thinking of soaking it in water and dawn dish soap overnight.

 

[ksp7498]

It's possible that the impact damaged the material inside the cat. An impact hard enough to tear apart a radiator would probably do a number on the honeycomb in the cat.

 

[2010Civic]

If cleaning the cat doesn't work what are your thoughts on going aftermarket?

I can get this one for $242
https://www.1aauto.com/2006-11-honda-civ...1917&y=2008

Or OEM is around double that.

 

[dgunay]

Have you tried lacquer thinner?

https://www.youtube.com/watch?v=5icTmYItwiE

 

[2010Civic]

No, but that seems like a bad idea that has potential to ruin a lot of things.

 

[BrocLuno]

CATs are ceramic matrix that live at 2,000 degrees. How is lacquer thinner going to hurt that ??

But really, cleaning a CAT is about blowing it backwards with low pressure high volume air to remove any ash cap on the inlet side. The ash caps form from oil consumption. If that does not do it, you need a replacement ...

When the motor fried, it may have taken the head gasket/warped head, etc. If there was any residual coolant in any pockets in the system, it might have flashed to steam and gone out the exhaust. Coolant and CATs are a one way trip to replacement town ...

 

[2010Civic]

Originally Posted By: BrocLuno
CATs are ceramic matrix that live at 2,000 degrees. How is lacquer thinner going to hurt that ??

But really, cleaning a CAT is about blowing it backwards with low pressure high volume air to remove any ash cap on the inlet side. The ash caps form from oil consumption. If that does not do it, you need a replacement ...

When the motor fried, it may have taken the head gasket/warped head, etc. If there was any residual coolant in any pockets in the system, it might have flashed to steam and gone out the exhaust. Coolant and CATs are a one way trip to replacement town ...



Couldn't lacquer thinner possibly hurt the fuel system or the engine? It's not worth it to me.

It very well could have warped the head. The engine seemed to have no compression.

 

[slacktide_bitog]

Walker and Eastern make good cats And you should replace the upstream oxygen sensors at the same time, too. Get Denso or NGK/NTK sensors

 

[SatinSilver]

+1 on Walker, I saw a price earlier for around $294. Stick with a name brand on this one or oem. I remember having a 1999 Accord and a new oem cat was $1200.

 

[GMBoy]

Buy some time and use spark plug non-foulers to extend the o2 sensor out of the exhaust stream. It works and I've probably done 30 of these "fixes" for P0420 and P0430 codes in the last few years. Google it and see.

 

[Gasbuggy]

Gallon of mineral spirits in a full tank of gas. Code won't come back for a long time.

 

[Vikas]

Originally Posted By: Gasbuggy
Gallon of mineral spirits in a full tank of gas. Code won't come back for a long time.
Did you find this on the internet or have personal experience to confirm this?

 

[2010Civic]

What would you guys prefer? A ebay cat for $140 shipped or I found a place that has a cat from a 2007 Civic, 157k miles, for $145 shipped. Or 1A auto has one for $240.

 

[nthach]

Stick with a good aftermarket brand(Walker, Eastern, CATCO) - some of those eBay cats do come from China or other places.

If possible, even though you don't live in CA get a CARB-compliant cat - there's more washcoat loading, and a better warranty. Do make sure there's no fuel system or ignition system issues, or you're looking at another new cat.