Intermittent P0420 vs. oil consumption advice please

Not sure how fast you drive, but many believe there is a correlation with oil consumption levels.

For your oil consumption problem, look into doing a "piston soak" and/or oil flushes with Kreen, BG EPR, b12 chemtool, etc (or insert your favorite solvent type product). If you have a few extra bucks, many outside of this forum have found positive results with an ester based oil change using Valvoline Premium Blue "Restore" (part# VVL 877377, it costs 70+ per gallon).

If you have a DIY attitude, you could try soaking the catalytic converter in citric and oxalic acids. It might buy you some time or miles.

Otherwise wait until you're up for another inspection, then buy and install a direct fit cat for a couple hundred.

Personally found that replacing my heavily used spark plugs with new, and replacing the fuel injectors (with reconditioned) to be of some help in mitigating my intermittent P0420, but that only lasted about 800 miles. Then I replaced the upstream A/F and downstream oxygen sensors (with OEM), which kept the P0420 at bay for 1200 miles, allowing it to pass smog. Still the code is back, full time now. I'll do a cat soak before the next smog inspection, or just swap in a new cat if the soaking proves ineffective or doesn't last long enough to pass the smog.

A highlight of replacing the two (2) sensors is the MPG went up around 10%, even with my spirited driving from coast to coast and back.

 

Did @m.wynn share his soaking strategy while you were in his neck of the woods.

Sucks that the labor we put into the sensors didn’t last longer.

But at least you’re good until 2021.

 

He sure did, right after we poured a Hoegaarden back along the river

Was kind of a breeze over all, though it always helps when you have the proper space/tools and an extra pair of willing hands

So true. Hoping it will clear itself up again.

 

I don’t know if anyone has used Caticlean in a Prius or not. I wonder what it would do to the fuel bladder.

 

Update: drove it another 600+ miles this past week, during which I cleared the logged codes and nothing has returned as of yet

If you've tried nearly everything else, it might be worth swapping out the old/lazy upstream A/F sensor.

 

I would say this rate of oil consumption is well within the range of "normal" for Prius and would not attribute the failing catalytic converter to this.

Have you tried using one of the high mileage synthetic oils to see if that helps reduce the oil consumption rate? I am currently using the Mobil 1 5W-30 high mileage oil on my 2007 with 134K miles. That might have some beneficial effect, too early to say for sure.

A great idea to change the iridium spark plugs and the PCV valve and to clean the mass air flow sensor. Make sure you do not damage the valve cover when removing the PCV valve. A couple of other posters reported doing so because they used the wrong tool for this job, striking the cover with their wrench. Use a deep socket.

I don't know about the overnight piston soak. You will not be able to rotate the engine fast enough via rotating the crankshaft manually, to get rid of liquid that may remain above the pistons.

It might work to try starting the engine with the plugs out, to get MG1 to rotate the engine. Disconnect the 12V battery after doing so to clear the engine no-start DTC P3190. Try this BEFORE you do the piston soak to verify that you can spin the engine with the plugs out.

OK. As previously suggested, you might gain more time on the original catalytic converter by replacing the upstream air/fuel ratio sensor with the correct Toyota part.