1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Worth replacing all iginition coils when I replace one?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Typingmonkey, Dec 14, 2022.

  1. Typingmonkey

    Typingmonkey New Member

    Joined:
    Jan 25, 2022
    12
    1
    0
    Location:
    97701
    Vehicle:
    2010 Prius
    Model:
    Two
    I had one cylinder #2 misfire at startup recently, after my Prius had sat for about a week in a cold garage. I read the many threads on here and will embark on some of the fixes and maintenance suggested.

    The car is approaching 180k miles, service history unknown (I acquired at 175k). So for my first pass I am planning on replacing all spark plugs and #2 ignition coil, cleaning intake and EGR pipe, replacing PCR valve.

    After I saw how much work is involved in disassembling the wipers to get to the coils and plugs, I started to think that maybe I should replace all the ignition coils while I'm in there. However, I balked at the $55/each price of the coils.

    What do you all think: Should I cough up the extra $165 and replace all four ignition coils, as long as I'm going through the work of disassembling everything to get to them?
     
  2. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    10,294
    1,774
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    I didn't pay anywhere near that and yes I replaced them as a set I did not use the cheapest on the planet but I did not use denseo replacements I almost never have in any coil over plug application had to use the dense replacements. I've had no trouble with the cheaper aftermarkets they seem to work fine I'll put 50 $60,000 on the latest set of in a 2013. And once you're used to changing them it's really not that bad you can change you can get the tray out and 36 minutes with the wiper assembly and then you're just dealing with four 10 mm bolts and a couple of plugs and the coil over plug extensions are out.
     
  3. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    24,882
    16,196
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    The wipers and cowl are just plain in the way ... so "take out wipers and cowl" is a starting step in so many different repair procedures, it's like "chop ½ onion" in recipes. Eventually you can kind of do it with your eyes closed. (Unlike the onions, it doesn't usually make me cry. It's just tedious.)

    I guess what I'm saying is I wouldn't use that by itself as a reason to spend extra money replacing stuff that ain't broke. You'll be taking the wipers and cowl out again for something else sooner or later anyway.
     
    Typingmonkey likes this.
  4. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    11,318
    4,610
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    In general electrical parts are more reliable than mechanical parts... Your car had one tiny moment of weakness and throwing money at it without being patient and waiting for more symptoms is most likely a waste of money. First step is to change the position of the coils and see if the misfire moves to another cylinder. Of course it's probably not worth until you get another misfire code. Or maybe this isn't a misfire code and you're assuming that's the problem even though it's perfectly normal for an Atkinson engine to run a little rough on start up if it hasn't been running in a while.
     
    Typingmonkey likes this.
  5. Typingmonkey

    Typingmonkey New Member

    Joined:
    Jan 25, 2022
    12
    1
    0
    Location:
    97701
    Vehicle:
    2010 Prius
    Model:
    Two
    Thanks for your input. I'm pretty naive, for sure! The engine went klunk klunk klunk klunk for more than a few seconds (seemed like a long time!) and the check engine light came on; I read the code with Dr. Prius and got P0302. I think that is definitive for a misfire; am I right?

    Replacing plugs and one ignition coil seemed like preventative maintenance that it's probably due for anyway...?
     
  6. Typingmonkey

    Typingmonkey New Member

    Joined:
    Jan 25, 2022
    12
    1
    0
    Location:
    97701
    Vehicle:
    2010 Prius
    Model:
    Two
    Ah, thanks for that input. Good to know.
     
  7. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    11,318
    4,610
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    Nope... First you have to determine the source of the misfire. If it's the coil, then when you swap the coil with the one next to it the location of the misfire will change. If it doesn't then it's not the coils, but something else. But before you even get to this point you have to have the misfire happen again to justify the time and effort involved in moving the coils to different locations.
     
    Typingmonkey likes this.
  8. Mendel Leisk

    Mendel Leisk EGR Fanatic

    Joined:
    Oct 17, 2010
    56,610
    39,191
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    @PriusCamper beat me to it, but anyways:

    try swapping the coils around, and see if the misfire code goes with the coil.

    If it doesn't, and considering the car has 180k miles, and no mention of previous EGR cleaning, the coils are likely fine, but you might be experiencing head gasket failure.
     
    Foxglove and PriusCamper like this.
  9. Typingmonkey

    Typingmonkey New Member

    Joined:
    Jan 25, 2022
    12
    1
    0
    Location:
    97701
    Vehicle:
    2010 Prius
    Model:
    Two
    I guess I was worried about damaging the engine so I wanted to do some preventative maintenance steps before it misfired again... but I'm very happy to not tear it apart prematurely!
     
  10. Typingmonkey

    Typingmonkey New Member

    Joined:
    Jan 25, 2022
    12
    1
    0
    Location:
    97701
    Vehicle:
    2010 Prius
    Model:
    Two
    The coolant level has not changed for months and the oil looks clean – changed it recently. The EGR cleaning looks like a quite involved process. But I guess I'll take @PriusCamper's advice and wait and see...?
     
  11. Typingmonkey

    Typingmonkey New Member

    Joined:
    Jan 25, 2022
    12
    1
    0
    Location:
    97701
    Vehicle:
    2010 Prius
    Model:
    Two
    So just a couple (final?) questions: am I correct in understanding that I should do nothing for now?

    Is there any maintenance I should do?
     
  12. Mendel Leisk

    Mendel Leisk EGR Fanatic

    Joined:
    Oct 17, 2010
    56,610
    39,191
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    You're likely on the cusp of head gasket failure, due to long-neglected EGR clogging, and that's what the misfire is due to.

    Again, I would first swap the coils around, see if the misfire follows.

    If it doesn't (and I suspect it won't), that rules out a bad coil, and then I'd do a boroscope inspection of the cylinders, with the coolant system pressurized, look for coolant teardrops getting by the head gasket. Pay special attention to cylinders one and two, which tend to be most problematic.

    Alternately, a leak-down test will also determine head gasket integrity.

    Basically what's likely happening is coolant is leaking into a cylinder, getting past the head gasket, overnight. When you start up in the morning, the (uncompressible) coolant gives the piston fits as it comes up in the cylinder. Leave it long enough, you can bend a piston arm, punch a hole in the block wall.

    And get on the EGR cleaning ASAP. See first couple of links in my signature.

    Or just trade it; it's likely to be a money pit soon.
     
    #12 Mendel Leisk, Dec 15, 2022
    Last edited: Dec 15, 2022
    Typingmonkey likes this.