P0420 code (possible lemon)

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Jul 13, 2020
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Hey everyone. I have an '09 Pontiac Vibe with the oil-burning Toyota 2az fe engine. 173500 miles. I've had the car for a few months now and it's burning a quart of oil every 1000 to 1200 miles. Just today my CEL came on for code P0420 (catalyst efficiency). I had a misfire code on cylinder 4 a couple months back, but changing the spark plugs seemed to have fixed that since I have not had any more misfire codes since. I also replaced the split/cracked ignition coil boots (can't tell any difference better or worse) I don't believe that means I don't have occasional misfires simply because I haven't had any codes. The car occasionally idles low, hunts for idle, and vibrates, but I can't tell if it's actually misfiring or not. I've tried a few different motor oils as well as Marvel Mystery oil in the gas and crankcase to mitigate the oil consumption problem to no avail. So, I have a few questions:
Are there any causes/solutions to this code other than the catalytic converter?
Could the MMO or other gasoline/oil additives have contributed to this code? (I've used several including redline, lucas, kreen, and possibly a little too much MMO)
Has anyone successfully reduced oil consumption for this engine without rebuilding it?
Can excessive oil consumption (blowby) cause this code?
Should I get rid of this car?
She always starts and runs reasonably fine. Everything else works perfectly.
Any thoughts and/or suggestions are greatly appreciated!
 
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The oil consumption and long term driving with a misfire likely contributed to the condition. The converter is usually the "victim" of a poor running engine and in most cases last the life of any properly running vehicle.
 
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Weak or malfunctioning O2 sensors can trigger P0420. A qt every 1000 miles is a lot of oil. Unless you need to pass inspection soon, I'd concentrate on the oil consumption.
 
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No P0430 code with that....?
Anywho, I’m guessing the Oil burning condition (along with that “rich” running #4 cylinder) took its toll on that 173500 mile Cat.
Just saying........
 
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Stop the additives. Keep running the vehicle and don't use synthetic oil. Make sure you up the viscosity a grade. You can reset the CEL.
 
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Change the PCV valve. Clean the MAF and throttle body. If that doesn't help consider changing the O2 sensors. Short interval oil change, and 10w-30 or possibly 10w-40 as outdoor temps allow, like spring summer and fall, and/or if you have mild winters. One of Toyota's best engines if you can make up for the short comings, do more research to include Toyota Nation forum to figure out whatever other preventative measures you may wish to consider.
 

Jonas

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Thanks for all the advice. the oil burning is due to low tension piston rings/clogged oil return holes. wouldn't heavier oil make it worse? I tried mobile 1 high mileage 5w30 and it was about the same consumption but with noticeable drag on acceleration. the engine is spec'd for 5w20. I replaced the pcv valve months ago with an aftermarket one. Today, I cleaned the original one and reinstalled it, but I don't know if it's oe or not.
 

JTK

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Like said, if it has been burning oil for some time, the catalyst is soured and you will get catalyst inefficiency codes.

Maybe I'm thinking of the wrong Vibe/Matrix engine, but I thought those 4cyls were about bullet proof aside from maybe the intake manifold gasket leak that would throw a lean code in cold weather and was an easy fix. We had a 2008 Pontiac Vibe base model in the family for ~7yrs/70K miles. I think it had the factory brakes still when it was traded in for a Camry. Nothing but fluid/filter changes and a set of tires.
 

Jonas

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Like said, if it has been burning oil for some time, the catalyst is soured and you will get catalyst inefficiency codes.

Maybe I'm thinking of the wrong Vibe/Matrix engine, but I thought those 4cyls were about bullet proof aside from maybe the intake manifold gasket leak that would throw a lean code in cold weather and was an easy fix. We had a 2008 Pontiac Vibe base model in the family for ~7yrs/70K miles. I think it had the factory brakes still when it was traded in for a Camry. Nothing but fluid/filter changes and a set of tires.
There was a 1.8 and a 2.4. I have the 2.4 and there was a lawsuit for excessive oil consumption, a warranty extension, and a TSB on how to rebuild the engine. The 2.4 2AZ FE from 2007 to 2009 or so had the piston ring/oil return holes problem. The problem didn't usually show up until after 80k ish
 
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The 2.4 was also used in the Camry, redesigned in 2007, I thought 2007 was the worst year for the oil consumption, then after 2007 oil consumption could have been due to other factors, but if it is the oil return holes in the piston, I would try several frequent oil changes with possibly(probably) using the Rislone product or some other within 500 miles of the next oil change.
 

Jonas

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The 2.4 was also used in the Camry, redesigned in 2007, I thought 2007 was the worst year for the oil consumption, then after 2007 oil consumption could have been due to other factors, but if it is the oil return holes in the piston, I would try several frequent oil changes with possibly(probably) using the Rislone product or some other within 500 miles of the next oil change.
Which Rislone product do you recommend?
 
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Like Supersonic noted change the PCV, and clean the MAF sensor and throttle body. Just use brake cleaner for the MAF and throttle body, changing the PCV valve is cheap and easy and may actually decrease the oil consumption. Generally excessive oil consumption is caused by worn piston rings so no adding or subtracting of additives or oil grades can really cure it. Excessive oil consumption is a common issue on the 2.4L 2AZ-FE, Toyota has an extended warranty on 07-09 2AZ's but it is limited to engines with <150K and <10 years of age. You might want to call up a local GM dealer to see if they have a similar extended warranty, sometimes dealers will cover a percentage of the repair work on a known issue extended warranty situation when the vehicle is over the cutoff. P0420 is 90% of the time a worn out cat, but you can anyways check the operation of the O2 sensor with a scan tool to see if it's the much cheaper O2 sensor or it's wiring. Excessive misfiring will wear out a cat quite fast, so it's possible your misfiring and P0420 are related.
 
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Rislone Engine Treatment, there's also a Rislone High-Mileage Engine Treatment. There's probably some other products that would be similar, my choice would likely be a Rislone for the last 500 miles before an oil change, but I think you could leave it in for the full interval if I remember the instructions right. I've used it in that way, half botttle for the 2005 4Runner, 294k, and the other half on a 2005 Camry, 205k, didn't want to overdue it and they probably didn't need it, but both had high mileage when I acquired them.
 
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