Catalytic converter advice

[Jonas]

Hey all. '09 Vibe Matrix 2az fe 2.4L (bad oil rings, oil consumption 6-800 miles per quart) 178000k. My catalytic converter is bad, most likely due to excessive oil consumption. The good news is the car runs fine for now and we don't have emissions testing in my state. Currently, it's only a minor inconvenience to reset my CEL once or twice a day to keep my car from going into limp mode. However, I'm not sure how much worse this condition will get or how soon. I also have to replace my spark plugs more frequently which is only a minor pain as well. I would just like to have your opinions on my options, which are as follows:
Replace the pistons and cat(most expensive, solves everything)
Replace the cat (don't know which one to get/how long it will last)
Live with it (keep buying lots of oil and spark plugs, doesn't seem viable long-term)
I've also heard of a way to trick the O2 sensor into keeping the check engine light off, but doesn't address other potential problems
Any opinions would be appreciated as always!

 

[cjolson140]

If the oil consumption started recently, you might be able to address it by doing a piston soak to soften and remove the carbon in the oil ring lands/drains. I had good results using Berryman’s B12, followed by an Italian tuneup. Are you fouling plugs or just eroding/wearing them out too quickly?

What do you mean by limp mode? I’ve had a couple toyotas set a p0420 code like yours, but it didn’t reduce performance or otherwise change anything (car still ran in closed loop, got the same power & fuel economy)

 

[Jonas]

You may be right about limp mode. It does turn my stability control off, but I haven't driven with the light on long enough to really tell a difference. I just clear the code whenever it pops up.
I've tried the piston soak and other remedies to no avail. The car was drinking oil when I bought it (thought it had a leak before I learned about the problem with the rings.) I started having misfires after about 5k on new plugs and the worst one looked like this:

This was before the piston soak, which did help with engine knocking/carbon buildup and allowed me to use 87 gas again. It had little to no effect on oil consumption, though.

 

[AutoMechanic]

I’d go ahead and replace the catalytic converter. Toyota’s don’t like to have power without them I know when my dads went out because of gas going through it we were going about 25mph on the highway it was not a good experience. I don’t see a reason to replace the pistons maybe replace the rings on them instead usually that does fine. I’ve changed rings many times on older Toyota and it usually doesn’t give any issue.

 

[cjolson140]

No stability control with a CEL? That sucks, I thought it was just Subaru’s that did that. I think with that much oil consumption, a new cat won’t last long. What is your driving cycle like? If you drive mostly on the highway, you might eventually improve things by doing more piston soaks and oil ‘treatments’ (Rislone, Kreen, etc) but it also may not help at all. Is your PCV blocked? (Idle should change if you open the oil fill cap while it’s idling)

Another way around the p0420 code is to get a spacer for the rear (post-cat) oxygen sensor, to remove the end of the sensor from being directly in the exhaust steam. This slows down it’s reaction time and often prevents the code from being set.

p0420 is set when over several drive cycles, the upstream and downstream oxygen sensors match each other’s output too closely, indicating poor catalyst oxygen storage ability. The computer wants to see the downstream post-cat sensor lag behind & demonstrate fewer ‘swings’ than the upstream sensor, which you may achieve with a spacer.

 

[mattwithcats]

First, gut the pre-cat...
The pre-cat is the coffee can shape just after the exhaust manifold.
Second, use a full synthetic 5W-30 diesel oil...

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Third, good old copper plugs. I like NGK V-Grooves...
Last, replace the catalytic converter with a universal....

 

[Jonas]

I should also mention I had a bad misfire from a broken spark plug that caused a flashing CEL shortly after I got the car. I didn't drive it much, but I had to drive it a little before I could fix it. I wonder how much that had to do with ruining my cat as opposed to the excessive blowby.

 

[Jonas]

One more thing. When I disconnect the battery to reset everything, the car runs great for a little while and my scanner says all the monitors are ready and okay (green check mark.) As I drive, the car seems to gradually run worse, slightly less power, rough idle, etc. Do Toyotas intentionally run worse when there is a trouble code for emissions? I can live with a CEL, but not running rough, sluggish, and worse gas mileage.

 

[slacktide_bitog]

Since the engine is relatively easy to access (like not a transverse V6 or half the engine tucked under the windshield), if you know how to replace the pistons and rings, you might as well.

 

[Jonas]

Since the engine is relatively easy to access (like not a transverse V6 or half the engine tucked under the windshield), if you know how to replace the pistons and rings, you might as well.

You know, I thought a job like this would be beyond my reach, but after talking to my mechanically inclined brother, he thinks we can knock it out in a weekend for under $1k.

 

[DGXR]

Keep us posted on the progress, and result! Good luck!

 

[jqgz]

Apparently you can clean a catalytic converter with dish soap if you can get it off the car. So maybe saw it off, soak in dish soap and water for a day, and band clamp it back on?