Been thinking that myself. I’m thinking oil issues caused the cat problem, not vice versa.

Should know more today about what's going on with the engine. I think the oil analysis is a good first step. Don't think oil is related to cat failure. Typical causes for cat failure are o2 sensors not working properly and over fueling.

The Cat failure caused the engine issue. Think of it this way. Engine is humming along flowing nicely at 55-60 mph, Suddenly the exhaust is shut off, where does the pressure go? How does that pressure affect the engine internals?

Thanks! I've been reading a lot of threads on that forum since the second issue popped up trying to figure out what the oil analysis might tell me.

http://forums.pelicanparts.com/uploa...1599226129.jpg


I have always been a data or information geek. Shortly after I turned 100,000 miles on my El Camino I got to wondering about the engine wear. I found a local oil testing company and I started testing and graphing the numbers with PowerPoint.

The biggest thing I learned right away was to change the air filter much more often. The silicon levels (sand and grit) were sucked past the air filter and grinding up the parts inside the engine. If you look at the chart, every time the silicon dropped was right after I put on a new air filter. I finally learned that after 100,000 miles of testing things were not going to blow up, and to change the air filter more often.

That engine went 300,000 miles before it was just worn out. $1,700 bought me a brand new, not rebuilt but new 350 delivered to me door. Can't beat the Chevy small block for price.

IIRC, high levels of zinc + high NOACK (evaporation) in low/mid-grade oils can kill cats. So if you can rule that out via UOA, then you can focus elsewhere. ;)

One is left wondering how a cat goes from 'humming along' to fully blocked in an instant.

There is more to the story, but without the cat you will never know.

Has the shop even pulled the pan yet to determine if your noise was a bad rod bearing?

Not yet. We're waiting on direction from Hyundai.

Yes one is. No drivability issues prior to failure. Never a CEL. Just one day BOOM cat is gone. The day the second one went he was literally 1/2 mile from home and it just lost power and wouldn't throttle up. The day it failed, he drove the car home from school about 45 minutes away, stopped at the house, then went into town and back. On the way back from town it just puked. The previous time he took off for Lima OH, on his way back the engine just stopped running. Again, no CEL no warnings of any sort.

Some of these modern engines with variable valve timing are using the vvt to perform the egr function. Holding the exhaust valve open under certain conditions to dilute the incoming fresh air fuel mixture to lower NoX. You get a lower quality cat converter substrate (Nissan had this happen among others) and it starts to break up and get sucked into the cylinder. This wears out the cylinder and rings and allows burnt oil to get into the cats, causing faster deterioration. It’s a vicious cycle. I highly doubt back pressure damaged your motor. I have had multiple LS based V8s in the shop with failed lifters not allowing an exhaust valve to open that have run for many many miles that way with no mechanical damage. Also they are designed to withstand insane combustion pressures. Also while it’s a much stronger diesel application, Jake brakes perform the same engine braking operation with no damage.

I work with airplanes (on the side) and we usually do an oil sample every 2nd oil change. Well worth the $$ to keep an eye on what is going on inside.

Results are in!

Iron 100 ppm universal average 7 ppm
Aluminum 90 ppm universal average 3 ppm

What did it say about brass, tin and lead ?

Lead and tin were zero. There was no line for brass included in the report.

points to not being a bearing issue then unless maybe the cam bearings are integral to the head.

I'm wishing I would have done oil analysis on the first two changes for a baseline. With the short block only having 9000 miles on it, I'm not sure how long to expect really high levels of aluminum, Iron and Chromium.

Forgot to list chromium. sample had 4 ppm baseline is zero for this engine.

Any fuel dilution?

Nope. No fuel or water noted in the sample.

Well, time to yank the pan and look at that rod.

That's what I'm thinking too.