Spark plug replacement - tools needed

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by tomiha, Jul 7, 2008.

  1. tomiha

    tomiha New Member

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    When you get ready at 100K miles or so, here are the tools you will need to replace your plugs on a 2005 or later model, did mine last night

    Added to posting on 7/8... Be sure to buy Iridium plugs and they will last another 100k miles. They are $16 ea. at the dealer (Denso) or you can get them at the auto store for $7 (NGK and others).

    10mm socket and rachet wrench
    5/8 " MAGNETIC spark plug socket
    4 to 6 inch extension for rachet wrench
    Spark plug anti-sieze compound (small foil package 99 cents at auto store)

    1. Remove relay from center of firewall and set aside (10 mm socket, 2 screws)
    2. Looking down on top of engine, you will see 4 black wires going into 4 assemblies (ignition coils) on the engine block, secured with one screw each. Starting at the left side, remove the screw (10mm socket) then lift the coil straight up while rotating slightly to free it from the spark plug. The plug is at the bottom of the hole you just incovered.
    3. Insert your 5/8" magnetic socket and the extension into the hole and it will center on the sprak plug (Magnetic is necessary to lift the plug when loosened). If it is like mine, the plugs will be fairly hard to get loose for the first several turns, as they have been in the hot engine for 100K miles. Don't give up, slowly loosen until you can lift them out. NOTE: If you use a 6" extension, you will have to wriggle is around to get the last two plugs out... it can be done, but a 5" would work better.
    4. Be sure to apply some anti-sieze compound on the new plugs before inserting!! I plan to get several hundred K miles on mine and I am going to be doing this again in a few years. When torqueing in the new plugs, you will feel the resistance from the old residue. Be sure to bottom them out. You should use a torque wrench.
    5. Repeat for the next two plugs, when you get to the far right plug, you will need to go to the next step.
    6. Last plug, far right on engine - on this plug, Toyota decided to not leave enough service loop on the cable to allow you to just lift out the coil, so you have to unplug it from the cable. Remove the bolt as you did on the other 3. With the coil in it's original position, there is clearance on the right backet for you to push the white connector off of the coil, once you get the release tab in the right position. I used a tiny screwdriver to push on the OUTERMOST end of the tab while gently pushing the connector to the right with a larger screw driver until it worked free and popped off. Then the process is the same as the rest of the plugs. The cable snaps back in easily. Hope you don't have very large hands though ;)
    7. Replace the relay and you are good to go. Took me less than an hour
     
  2. rumpledoll

    rumpledoll Member

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    What is the condition of the old Iridium plugs like at 100,000 miles?

    I just changed the OEM platinum plugs on my 2002 Ford Explorer at 60,000 miles and they were all out of gap specification by 0.007" (should be 0.052" - 0.056", all were at 0.063"). According to the owners manual on the Ford these plugs should be good for 100,000 miles but given their condition at 60,000 miles there is no way they would make it. An interesting aside, the Ford also had different plugs in each side of the engine, neither of which were the double Platinum spec'd in the manual! Great QA there Ford.
     
  3. tomiha

    tomiha New Member

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    I did not measure them, however the gap was visually greater than the new ones. Guessing between .005 and .010
     
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    This is intentional. The double Platinum plug model is utilized when you replace the original equipment plugs.

    The original equipment plugs are different on each bank for the following reason: The Ford ignition system fires two plugs at once, using one center-tapped ignition coil to fire both plugs. This saves some minor expense with the engine ECU.

    However, the result is that the voltage polarity applied to one plug is opposite that applied to the other plug, with respect to vehicle ground. Hence the plugs installed on one bank need to have the platinum tip on the center conductor, while the plugs installed on the other bank need to have the platinum tip on the ground conductor.

    Prior to buying my HiHy, I owned a 1997 Explorer XLT V8 AWD and replaced the platinum plugs at ~90K miles. What a PITA; I had to remove both front tires and access the plugs through the front fender liners. Scraped a few inches of skin off one arm when a spark plug wire refused to disconnect from the plug, then suddenly let loose when I pulled hard... I had to replace all of the spark plug wires since the connectors were in bad shape. Too bad Ford did not use dielectric grease on the connectors...
     
  5. jayman

    jayman Senior Member

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    My FJ Cruiser also came with different brand plugs from the factory: NGK driver side vee, Denso passenger side vee. Dealerships replace with just Denso's. I used NGK and it works fine

    Could be just a supplier agreement in the case of the FJ
     
  6. rumpledoll

    rumpledoll Member

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    Thanks Patrick - I did a Google search on this issue but you were the only one with an explanation! I thought it odd that one side had the Platinum on the center and the other on the ground side. I replaced 'em with double platinums which should last at least another 60,000 miles.

    Given the troubles that some plugs have in aluminum heads coming out after a long period of time, I do not think I'm going to let my Prius go 100,000 miles on the OEM plugs. Most likely I'll pull 'em at 80,000 miles or so and replace them with another Iridium set.

    Rumple
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    This is a good idea. I removed the plugs on my 2004 at 30K miles for inspection (and to make sure there was no water in the spark plug wells), put a bit of antiseize lube on the threads, reinstalled them, and cleaned the surface dirt off the tops of the igniters.
     
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  8. sparkymarvin

    sparkymarvin Member

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    I feel silly asking this, but...
    Do the Denso plugs come pre-gapped, or did you require a gapping tool during your work?
     
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    No need to feel silly, this is a very reasonable question as the spark plug might be used in more than one engine model.

    I set the gap to 1.0 mm. The factory-set gap is bigger than that.
     
  10. sparkymarvin

    sparkymarvin Member

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    Thank you for the reply.
    I am curious why you chose 1mm.
     
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The spec is 1.0 to 1.1 mm, so I set the spark plugs at the narrow end of the spec. Presumably they will remain in spec longer, by starting at 1.0 mm.
     
  12. sparkymarvin

    sparkymarvin Member

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    Thanks for the info.
    I just got in from changing my plugs.
    I discovered that it is also a great time to replace the PCV valve since the wire harness is tucked out of the way.
     
  13. HAFGAST1

    HAFGAST1 New Member

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    Your directions are quite precise - made it an easy 1/2 hour job. The "resistance" is not from residue but is the compression seal seating. Recommend Advanced Auto Parts magentic socket #80546($10.29) which has a swivel extension as part of the tool. Add a 3" extension to this and it's the perfect length. My '04 Prius had 130K when plugs changed; wouldn't recommend going any farther - they were very well eroded.
     
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  14. tnthub

    tnthub Member

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    Nice writeup on changing plugs.

    The only thing I would add from my own experience is to avoid platinum plugs because the pucks sometimes fall off and to always check the gap because sometimes the factory set gap is not correct. I tend to always make the gap a bit tighter than factory settings just for reliability...
     
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  15. ggcc

    ggcc Member

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    I think amazon.com is having good price for spark plugs.
     
  16. tf4624

    tf4624 Active Member

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    Takes max 10 min to do it
     
  17. Ryanpl

    Ryanpl Active Member

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    my dealer told me that i need to have my spark plugs relpaced, which I plan on doing myself once it gets warmer. He also mentioned that I need new spark plug wires. Does anyone know the oem part for the wires?
     
  18. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Prius does not have "spark plug wires". Each spark plug has its own igniter, which sits directly on top of the spark plug. Hence no high voltage wiring is needed.
     
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  19. F8L

    F8L Protecting Habitat & AG Lands

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    Did he tell you
    . :D
     
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  20. Ryanpl

    Ryanpl Active Member

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    FL8, that guy looks nothing like my "Service Advisor" aka salesman. My guy looks slicker.
     
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