P0301. Replaced coil & spark plug, now it's returned.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by SicilianDragon, May 1, 2021.

  1. SicilianDragon

    SicilianDragon New Member

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    So...something like this?


     
  2. AW82

    AW82 Member

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    That's what Chapman was saying is not a great tool. This would be a better choice:
     
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  3. SicilianDragon

    SicilianDragon New Member

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    Oh ok, I didn't recognize it as the same one out of context.

    That better one is not a whole lot cheaper than having a mechanic test it...but like I said, I guess it would be best to do it myself.
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Mechanic has the know how too, tips the scale?
     
  5. AW82

    AW82 Member

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    What's the labor for a mechanic to remove the wipers, cowl, etc. in order to replace the spark plugs? And how long does a leakdown test take on top of that spark plug access labor? An additional half hour? Would all that really be cheaper than $70?
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Good points.

    You could DIY wiper/cowl removal. One good reason: you’re gentler on the components; the one time dealership had ours off they managed to scrape the wipers, had them on concrete then STACKED other bits on top... :mad:
     
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  7. Grit

    Grit Senior Member

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    not bad. Took mine to a tire shop to rotate tires. Heard screeching then half hour later heard the screeching again pulling up to the main entrance glass door, it was my car. Got in and the parking break has half engaged. The red BREAK led was on the entire time.
     
  8. Grit

    Grit Senior Member

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    o_O
     
  9. SicilianDragon

    SicilianDragon New Member

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    I didn't say a mechanic was cheaper, just that the kit "wasn't a whole lot cheaper." Because the better quality one was about $80 w/ tax and shipping, and the quote for a diagnosis was $98.

    Replacing the spark plugs isn't included in the test...but I did have the mechanic (referenced earlier in the thread) replace the spark plug and ignition coil for only $70.

    I still would pick the kit over the mechanic. Did you purposely delete the link to the more expensive kit? I am still interested in it and would like to see it again if that's ok...thanks.

    -------EDIT: It's showing up on my screen again. Got it saved now.
     
    #69 SicilianDragon, May 6, 2021
    Last edited: May 6, 2021
  10. SicilianDragon

    SicilianDragon New Member

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    I don't know...I was pretty put off by the guy yesterday. It's so common for people to say "head gasket" over and over, as if they're smirking and saying "tough luck that you have to spend $1K you don't have." I have no reason to believe they wouldn't pretend it's the head gasket no matter what it is, because they want as much money as possible.

    Hopefully the leak-down test isn't too complicated. Seems pretty black-and-white: either I get the correct results or I don't. I won't be doing the actual repair work myself.
     
  11. AW82

    AW82 Member

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    That seems pretty good. A lot of people have paid $150 or more for spark plug replacement (so ~$120 in labor) because of the time it takes to remove the spark plugs because they're hard to get to. Not like some cars (many Hondas) where you can literally replace plugs and coils in less than 5 minutes.
     
  12. ChapmanF

    ChapmanF Senior Member

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    Of course you need an air compressor as well as the leakdown tool itself. Getting the reading is pretty simple, and then if it shows more than the usual small leakage, you make a bit of a judgment call how bad it is, and you listen around the engine for where the air is going, and that should give you a diagnosis.

    If it doesn't show you any smoking gun, you haven't wasted the time; you write your readings down and now you've got a baseline to compare to later readings down the road.

    For some reason, lots of video sources say weird things about holding (or not holding) the cylinder you're checking at TDC during the test. Some of them use a wrench to turn the crank around to position and then take the wrench off and "hope" the air won't spin the engine when you do the test. That's goofy, of course the air will spin the engine, unless you have some sort of magical ability to set pistons at perfect TDC (and you balance pencils on their pointy ends just for kicks).

    One video I watched said they were taking the wrench off so it wouldn't fly around and break your hand or damage the car. Well, right, you can't leave the wrench there loose and let it fly around! But if you take it off, nothing is stopping the engine from spinning when you do the test.

    I typically just turn the crank till the piston is up near TDC, and I have the socket on a breaker bar that I can position on the crank bolt so the breaker bar handle is snug up against something under the hood, and maybe lash it there with a strap, or its end is resting on the ground, and I put my foot on it.

    Because piston TDCs in a 4-cylinder are all 180° apart, and a hex bolt head doesn't look any different turned 180°, once you find a position for the breaker bar that works for one cylinder, you can use it for all of them.

    Some of the videos seem to be making it harder than that....
     
    #72 ChapmanF, May 6, 2021
    Last edited: May 6, 2021
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  13. SicilianDragon

    SicilianDragon New Member

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    Yes, he's definitely a bargain mechanic, but still honest and competent. Referred to me by another UberEats Toyota driver long ago. The drawback: he's from China so there's a language barrier; he can't explain "probable causes" when I talk to him. And he says he doesn't do anything as intense as HG replacement.
     
  14. SicilianDragon

    SicilianDragon New Member

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    Well thanks...simple is good, especially for those of us with no mechanical background.

    I do now recall that I'd have to take off the windshield rotators, etc. That's what the original mechanic charged $20 extra for.

    I believe you said there were eight possible results for the leak-down test. And again, I see no signs of a leak. Do you know: are there multiple results (out of the eight) that don't involve any leakage and/or don't show any smoking gun? And are all of the possible results pretty good as far as giving a probable solution?
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

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    Eric was saying it should be TDC of compression stroke, and he shows some trick for determining that. Anyone know why that would be; presumably to ensure all valves are closed?
     
  16. ChapmanF

    ChapmanF Senior Member

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    Right, you need it near TDC of the compression stroke to ensure the valves are closed, otherwise you're not doing much of a leakdown test.

    To have it exactly at TDC on that stroke would be one (unrealistic) way of making sure the test doesn't spin the engine; you can try it if you're good at balancing pencils on their points. More realistically, just get it pretty close to TDC and block the wrench in place.

    Some videos show the tech feeling for air at the end of the tester hose, to tell whether the TDC is on the compression or exhaust stroke. Air will come out the hose more forcefully on the compression stroke, because it hasn't got anywhere else to go. (Unless, of course, there's really severe leakage.)

    Some also show a dipstick or something into the spark plug hole to identify when the piston is right at TDC, but if you look closely at the timing cover and the crank pulley you find they also put handy marks there for that. (The marks don't work for the cylinders that are second and fourth in firing order, but TDC for those is exactly 180° from where the marks are. If you found a good place to block your wrench for the cylinders where the marks work, the same wrench position will work for the other two as well, by symmetry of the hex bolt head.)

    I don't think that was me; I'm not sure what the "eight possible" results would be.

    The test will give you some nonzero leakage result for every cylinder. No engine ever built has zero leakage.

    Once you have leakage results for all four cylinders, you can start making some judgment calls. One is whether the leakage results are larger than they ought to be, and one is whether they're more different than they ought to be. (You can also look for possible patterns, like, are there two cylinders that both show high leakage and are physically adjacent.)

    If you find excessive leaking, or excessive difference, you can start drilling down into what the cause might be. Listening for where the air goes gives you a good start on that.

    Or, if you find that the readings are fairly uniform and they're all about as good as you'd expect for an engine of this one's age, miles, and condition, then that's also a useful diagnostic result, the kind that tells you there probably isn't a sealing issue and lets you move on to other possibilities to explain your driveability issue. As a side benefit, you can write down baseline leakdown numbers for this engine at this mileage, and use them for comparisons later to keep track of how the engine is holding up.
     
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  17. Mendel Leisk

    Mendel Leisk Senior Member

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    O’l Eric, in the absence of functional gauge, gets a fair bit of mileage just listening and looking, to determine the how and where. IIRC he adds smoke to the compressed air too.
     
  18. AW82

    AW82 Member

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    He's not perfect, but he's sure helped me out in the past...especially with Honda K24s.
     
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  19. ChapmanF

    ChapmanF Senior Member

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    Sure, his videos don't seem to be either perfect, or perfectly awful either. If he made a particularly good one on some subject I'd link to it; if somebody else made a better one I'd link to that.

    It does seem like he has somehow mastered self-promotion better than other folks, just from the way his videos often show up in search results above others that present the subject better.
     
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  20. wheezyglider

    wheezyglider Active Member

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    The ETCG video saved me from buying that useless cheap HF tester a couple years back. Thumbs up from me!
     
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