Catalytic Converter Issue..In California of course....

Some have successfully used Citric acid and Oxalic acid as a soak, though your mileage may vary.

Please report back in this thread or the other with any findings or successes.

 

@m.wynn has successfully done this several times.

Maybe he'll share his story and his brew.

 

In their Advanced Emissions and Driveability Diagnosis (T972) course, Toyota writes, “[T]he most common cause of catalytic converter failure is contamination.” This contamination is caused by problems elsewhere in the engine or emission control system, not by a defect in the converter itself.

The most important thing you can do to maintain the catalytic converter is to promptly detect and correct such malfunctions. If the car is consuming engine oil or coolant, making smoke or unusual odors, or the malfunction indicator (Check Engine) light is on, investigate at once. Don’t let the engine misfire, burn oil or coolant, or use a fuel/air mixture that’s too rich, for example, even for a short time.

 

Remedy for an oil burner is not cheap. A short block?

 

@dirt657 This x10. If the car isn't running right, you stop operating, no limping it along.

It means checking the dipstick more, tracking oil & coolant disappearances and fuel economy, preferably in a log of some kind. You see anything go out of the baseline, stop and fix it. Do it that way and you can have an heirloom converter fit to pass on to the next generation.

 

Let's not go too far into the deep end of the pool.

Our old 2010 with over 200k miles consumed a quart of oil from 125k miles onward and at some point would that have been enough to coke up the cat: probably

Just because the Prius consumes oil does that mean I need to tear into the inerds of the engine and fix it: not this guy

If you can understand the problem and then game plan when a problem arises: a good idea and way to proceed, depending on the circumstances

I'm pretty sure @m.wynn 's Gen2 he's been babying along through the NY inspection isn't burning oil, or if it is, not at a large amount. So an annual soak in a bath to pass inspection and keep a fuel efficient car on the road: makes sense to me

The OP is asking for ways to deal with the issue, so while stopping in your tracks and getting to the bottom of it is one way, it's not the only way.

 

Yeah, "some" oil burning is an automotive fact-of-life Where to draw the line.

 

While I do not have all the details, here is a pic of the setup:



Use whatcha got.

 

When you say "citric acid bath" do you mean a citric acid cleaning solvent, like Citrol, or do you mean laboratory grade, like anhydrous citric acid?

 

@dirt657, If your cat issue is simply early-stage P0420, there's a good chance the citric/oxalic soak will get you thru smog. I've used it twice now with a ~207k mile '07, and the results ***for me*** have been heart warming. This car burns around 3/4 qt of oil per 5k miles. We're talking NYS emissions inspection here, so OBD II monitor parameters being met is the hurdle.

March 2019, the car started the classic intermittent P0420 @194k miles and within a couple weeks it was hard-set. Clear the code and it would re-set again within a drive cycle or two. After the soak, the cat monitor set thumbs-up in about 5 minutes drive time, no P0420 pending. The car was daily driven for a couple weeks then passed emissions May 2019 at a tick under 195k.

Fast forward to early April 2020, P0420 again just shy of 206k. Performed the exact same procedure, again with the cat monitor setting almost immediately into the first test drive, passed NY emissions on April 21.

A consideration for you is that if you're having this issue with a turd gen, you will be draining (or at least disturbing) your engine coolant loop to pull the cat. The upside is that it's a simple loop to refill/bleed, and ***in my opinion*** doesn't hurt anything to keep fresh coolant in these head gasket munchers.

In this thread:

Oil Contamination - P0420 Cat Replacement? | PriusChat

@BigVanMan does a nice job citing the internet famous Spanish study the formula is based on, and explaining his execution. I will say ***in my case*** the formula may be quite loose. Please do your own "calculations" with whatever product(s) you end up using.

I use the following, heated as close to 160 degrees F as possible for 6 hours, tap water (distilled is the rec, I believe):

Ball Citric Acid (5 tbs/gallon water)
Thompson's 3 in 1 Wood Cleaner ~10% oxalic acid (16 oz/gallon water)
Coleman propane camping stove
12" high stock pot (this height just about sinks a gen 2 cat, turd gen variation unknown)


The pic in Ray's post #10 is indeed my setup. Good luck, should you proceed with this hack...

 

The cat converter is an amazing catalyst and it is deactivated by "temporary" poisons like sulfur, and more permanent poisons like zinc phosphorous (ZDDP) from the lube additives. Maybe also carbon not sure. The cat will be more active at higher temps.

Those of us outside CARB can use a cheaper replacement, so it is more an issue for CARB states. So the citric acid soak helps remove the ZDDP contamination. I have often wondered if there are other easier approaches, such as using lubes with less ZDDP, might help to bring back activity. Also maybe a tiny trace of platinum in the lube oil could help. I don't know if there is a hack to increase converter temp, which sounds a little dangerous, but we used to have a Gen2/3 thermistor hack that allowed the Prius to get into stage 5 faster and thereby increase MPG in the warm-up period. Maybe the opposite of the thermistor hack would keep the converter in a more active mode, at the expense of lower MPG.

 

I'm no stranger to cooking the books, but cooking the exhaust is beyond my comfort zone.

(Although oilconsumption is starting to worry me 280k km (175k miles). I regularly add about a quart (1 liter), but don't know exactly how regularly, I guess once every few tanks (@500miles per tank), so a quart per 2000miles? Still below m.wynn, and no faultcodes that I am aware of.)

 

To update my post #12, year 2 of using the citric/oxalic soak to beat back the P0420 was effective for almost 9k miles, with the code setting at 214,500 miles.
The car is currently in Victor, Idaho, and it's unclear if it will return to New Yorkistan or not this spring. But even if it doesn't, my wife's '05 has 170k miles on the original cat. When the times comes, the soak must go on!