Intermittent P0420 vs. oil consumption advice please

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by dbailey, Jul 17, 2019.

  1. dbailey

    dbailey Junior Member

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    Thanks for all the great info on this forum concerning P0420.

    My 2007 Prius with 235k miles is pitching an intermittent P0420 alone. It burns about 1 L of oil per 3k miles. I intend to try OxiCat and/or CataClean to see if they have any positive effect, but I'm realistically looking at a catalytic converter replacement.

    Does anyone know the rate of catalytic converter clogging vs. volume of oil burned? I am not willing to invest in an engine rebuild to stop the oil consumption due to the age of the vehicle, so I'm trying to determine if putting a new converter in will buy me approximately 2 years. I drive about 15k miles/year in both city street and highway conditions.

    I'm in Georgia (near Atlanta) and have to pass yearly emissions inspections (they do not perform an exhaust test but they do check for current and recent codes). I am not interested in the trick method of spacing out the downstream O2 sensor.

    Thanks in advance for any advice you good people might lend.
     
  2. SFO

    SFO Senior Member

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    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.
     
  3. Raytheeagle

    Raytheeagle Senior Member

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    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(y).
     
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  4. SFO

    SFO Senior Member

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

    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.
     
    #4 SFO, Jul 18, 2019
    Last edited: Jul 19, 2019
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  5. Skibob

    Skibob Senior Member

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

    SFO Senior Member

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

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

    dbailey Junior Member

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    I’m not certain on the bladder vs CatiClean or OxiCat. I might email the companies to see if they know anything.

    I purchased plugs, MAF cleaner, a PCV valve, and some MMO today. I’m going to do an overnight piston soak. The only step I’m not quite sure about is how to get the engine to turn over to blow out any possible remaining fluid before putting the new plugs in. Will hitting the power button and waiting even work since the ICE doesn’t start up initially? Is there a crank bolt?

    I figured I would change the PCV while I’m in there. Is there any recommendation against doing this?

    Thanks everybody.
     
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  8. dbailey

    dbailey Junior Member

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    Oh yeah and in the meantime, the catalytic converter code hasn’t come back yet...
     
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    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.
     
    #9 Patrick Wong, Jul 28, 2019
    Last edited: Jul 28, 2019
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  10. dbailey

    dbailey Junior Member

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    Excellent advice - thank you very much. I'll post here when I finish up.
     
  11. dbailey

    dbailey Junior Member

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    Well I chickened out on the piston soak for fear of hydrolock. But I pulled the air filter box and cleaned the MAF sensor, changed the plugs, and changed the PCV valve. The plugs were fairly dark and sooty, and the PCV valve was gunky but still shaking a bit. I didn't have a torque wrench so I just made the plugs snug without overtightening (I hope). Anyway, I can tell a noticeable difference in the smoothness of the ICE, and it doesn't seem to clunk as dramatically when it shuts off as it was doing. I have not noticed any change in gas mileage (I average in the low 40s but I don't baby it at all). I'll keep an eye on the oil consumption and if these maintenance items don't help, I'll pull the plugs and try the MMO soak IMG_3502.JPG IMG_3503.JPG .
     

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