Replace spark plugs?

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by rioe, Jun 22, 2020.

  1. rioe

    rioe Junior Member

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    I was just reading in the maintenance manual about how Toyota recommends replacing spark plugs every 120K miles.
    I am at 120k now and have no obvious symptoms that would suggest I need to. Car is running fine.
    Is there any reason for me to replace them now or is it ok to wait until I notice an issue?
     
  2. PriusCamper

    PriusCamper Senior Member

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    I replaced mine at that mileage and they still looked new and wished I had waited... But more important next time you're under the hood spend 15 minutes pulling a plug and see what it looks like. You can learn alot about engine health by looking at a spark plug.
     
  3. AzusaPrius

    AzusaPrius Member

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    Well you will get better mpg with new plugs since the ones in there have 120k on them.

    Posted via the PriusChat mobile app.
     
  4. royrose

    royrose Senior Member

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    In California the interval is 150,000.

    From a footnote in the service manual: "For vehicles corresponding to PZEV the replacement interval is 150,000 miles".

    That, to me, suggests that they can go 150,000 everywhere but the standards are different for CARB vs CARB states.
     
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  5. TMR-JWAP

    TMR-JWAP Senior Member

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    A spark plug has a very simple job in life. Provide a spark when told. As long as that arc forms and the fuel is ignited, it's doing it's job. New or old really makes no significant difference with the thin wire iridium models (especially models with the extra disc on the ground electrode).

    On the other hand, if a plug is failing and causing misfires, the engine will obviously be having some problems. The one time I had an iridium plug start misfiring, it came on pretty quick. I was glad the car was local and was able to be limped home. It ended up being due to the 'disc' coming off and the ground electrode had extreme wear. The other 3 plugs? I keep them on the shelf as spares just in case. It would definitely be worth the time to at least remove, clean and inspect them. They could very well be ok for many many more miles. Or just replace them while they're out.
     
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  6. Driver900

    Driver900 New Member

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    I replaced the spark plugs in my preius-c 2012 and air filter, when ever I am going at slow speed the car shakes a bit like is going to stolled, any ideas what could be?
     
  7. PriusCamper

    PriusCamper Senior Member

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    Double check your work...
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    1. Did you check the spark plug gaps? They should be properly gapped out-of-the-box, and it's not recommended to try adjusting them. Still, it's good to check initially, just to ensure they're not damaged/dropped.

    2. What did you torque the plugs to? Or you used seated plus 1/2 additional turn, some method like that?

    3. Did you put any lubricant on the spark plug threads?

    4. All the spark plug coil connectors seated pushed on properly?

    5. What spark plugs, and where did you get them?

    6. This was engine air filter you replaced? Toyota brand or?
     
  9. royrose

    royrose Senior Member

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    OK, you've convinced me. I'm not changing mine ever! :sneaky:
     
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  10. rioe

    rioe Junior Member

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    I thought it’s just a matter of getting new spark plugs and throwing them in there. How important is the torqueing?
    what do we torque it to? Where do I buy the required torqueing tool?

    What kind of lubricant do you recommend putting on the plugs? And is lubricant a must?

    What kind of spark plugs do you recommend?
     
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  11. icspots

    icspots Junior Member

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    And changing engine oil is just a matter of pouring the oil on the top of the engine. It doesn’t matter if it’s an easy fix/repair/service, it still needs to be done correctly.

    It’s always a good idea to torque to the correct amount for the fastener you’re using. Too tight and you could strip the threads. Too loose and the fastener may come loose.

    Spark plugs are usually in the mid-teens ft/lbs. The prius should be about 13 ft/lbs.
    As mentioned above the poor-man method is make it hand tight, then another 1/4-1/2 turn with a wrench.

    You can purchase a torque wrench at most hardware or automotive stores, amazon, etc. They’ll run you from about thirty to several hundred dollars depending on the wrench, and the torque range it can be adjusted to.

    You should put anti-seize on the threads of the spark plug to make sure you can get it out next time. Generally use a die-electric grease on the contact point of the coil pack to the plug as well to ensure moisture doesn’t get in.

    Might you be fine without it? Sure. Is it cheap insurance? Absolutely. You can get little packets of grease and anti-seize at the auto parts store for a few dollars. I’ve had the same tiny tube of grease for three of my cars for years.... you don’t use much. I just recently bought a jar of anti-seize as I was doing a bunch of suspension work, so I’ll be using that for basically the rest of my life.

    I’m a big fan of NGK iridium plugs. I’ve had issues with Bosch plugs in the past, or the “fancy” ones with multiple firing tips.
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    @icspots Thanks for the response, I'd missed this. I'll take a crack at it too:


    1. Quite important. The plugs are steel and the head is aluminum, you don't want to overdo it.

    2. Owner's Manual (sadly) doesn't specify. You could check online at Toyota Tech Info. I don't have Prius c Repair Manual, but I do have 2nd gen, and I believe the c is using a second gen engine, maybe with some mod's.

    FWIW, 2nd Gen Repair Manual says 13 foot/pounds. It makes no mention of a lube on the threads, so the strong assumption would be that torque value is with clean/dry threads.

    3. Any automotive store would have torque wrenches. For a value like 13 foot/pounds I'd recommend a 3/8" or 1/4" drive wrench. You don't want to use a heavy duty 1/2" wrench, that barely gets down to 13 foot/pounds; best to use a wrench where the value you need is a little further up the scale. Torque wrenches tend to get increasingly inaccurate at their extremes, in particular the lowest values.

    I've always bought relatively cheap (heck, really cheap) wrenches, and I think I've been lucky. I recently checked them with a digital hang scale hooked onto the handle, and they all seem to be in the ball park. Not good enough for pro work, but ok. I have 1/4", 3/8" and 1/2" wrenches. Got the 1/2 many decades back, the 3/8 about a decade back, and the 1/4 just in the last year or two. The latter is good for very light duty fasteners, like the studs on 3rd gen EGR for example.

    4. If you use a lube anti-seize is recommended. Toyota makes no mention of lube. Various spark plug manufacturers either make no mention or advise against it. If you use anti-seize, I would suggest to put it on sparingly but thorougly. What I like to do is keep an old tooth brush around, that's got a bit of anti-seize on the bristles. I barely ever "reload" it, it's just got a trace. Brushing the threads thus you get just a thin skin. Also, if you've applied such a lube, I'd drop the torque value, to say 10~11 foot/pounds.

    5. No, lube is not mandatory. Maybe safest to not use it too, since it does sort of mess up the torque value.

    6. That's easy, the correct plug is specd in Owner's Manual:

    upload_2020-7-30_7-20-53.png
    (page 501)

    Also check with dealership parts department, in case Toyota's made a revision. With counterfeit plugs being sold on the net, dealership parts department would be safest bet for getting correct, genuine plug. FWIW, I typically buy from a very reputable local automotive specialty retailer when I need plugs; they're invariably cheaper for the same plugs.

    I've attached 2nd gen Repair Manual excerpt on plug install, fwiw:
     

    Attached Files:

    #12 Mendel Leisk, Jul 30, 2020
    Last edited: Jul 30, 2020
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