spark plug replacement

[TucsonPrius]

Since I just passed 40000 miles, I thought it would be a good time to swap out the spark plugs. Now, I know that the iridium plugs should be good for 120000 miles, but I was far more worried about the plugs being "welded" in place by that time, so out they came.

Overall, not too hard to do. Basic steps are as follows:

Disconect negative battery terminal (Personally, I'm not sure why, but the manual has this step). This can be a little bit difficult to get to, but a 10mm box end wrench did work.

Remove the relay box above the plugs and move it out of the way. Here I used a 10mm socket with a 2inch extension.

Disconnect the wires going to the ignition coils. This can be a bit difficult, as you have to press pretty hard on the lever thingy to get it to release. I had to use a small flat screwdriver on one of them to "help out a bit."

Remove the bolts holding each ignition coil (1 per). Again, a 10mm socket with extension. I only had a 2in extension. A 1 inch extension or a deep 10mm socket probably would have worked better.

Pull off the ignition coils.

Remove and replace each plug. Torque to 13 ft-lbs. These were a bit difficult to remove, so I'm glad I did it now. There was little wear on the plugs themselves, and they had discolored to a light grey. Here, use a 5/16 spark plug socket with an extension. I used a 6 inch extension which was a bit long and made it a bit tricky to get the plugs in and out, a 4 inch extension would probably be just right. I did not use any anti-sieze lubricant. The Toyota manual didn't say either way, and I had read a few bad things about it on the internet, so I went without.

Replace the ignition coils. Replace the bolts holding them. Torque to 82 in-lbs.

Reconnect the ignition wires. This is far easier than removing them. Just slide them on until you hear a click.

Replace the relay box. and torque to 53 in-lbs.

Reconnect negative battery terminal. Reset auto window, radio presets, and clock.

Clean up and test drive. As would be expected, no change in performance, but that's not why I did it.

Time from start to finish was about an hour. Cost was a little over $40 for the 4 plugs (part number 90919-01217, and $10.37 each from a local dealer).

Just thought I'd write it up in case anyone else is thinking of doing it themselves.

Thanks,
Shawn

[glenk]

<div class='quotetop'>QUOTE(TucsonPrius @ Jun 17 2006, 01:35 PM) [snapback]272745[/snapback]</div>

Remove and replace each plug. Torque to 13 ft-lbs. These were a bit difficult to remove, so I'm glad I did it now. There was little wear on the plugs themselves, and they had discolored to a light grey. Here, use a 5/16 spark plug socket with an extension.

I did not use any anti-sieze lubricant. The Toyota manual didn't say either way, and I had read a few bad things about it on the internet, so I went without.

[/b]

Thanks for sharing your experience!

I wanted to confirm the spark plug socket size listed above. I have the standard 13/16 and 5/8" sockets.

What have you heard bad about anti-seize? They absolutely require it for O2 sensors. I've been using molybdenum disulfide on sparkplugs for aluminum heads for years.

glenk

[TucsonPrius]

You right! It's a 5/8" spark plug socket. (5/16" would be pretty small, wouldn't it?)

In a couple of places I read that the anti-seize can drip down onto the plug and cause mis-firing. I also know quite a number of people recommend it, too. I just don't know, for sure. Since Toyota didn't say to use it (in either the manual or the commercial brochure they provide at mytoyota.com) I went without.

Thanks,
Shawn

[hobbit]

This task is made much easier by taking the black cowl piece out from
above the engine first. See http://priuschat.com/index.php?showtopic=20878
.
And if you left the plug threads completely dry, you're just going
to create the same problem you were trying to avert. Definitely get
some anti-seize or at the very least a little oil on those suckers.
.
_H*

[jreed]

Just recently got a Prius, so I'm a little late to the party, but I wanted to say thank you for this excellent information about spark plug removal and replacement. I bought the Prius 2001-2008 Haynes manual last week and (though it has photos of a couple steps), it doesn't contain as much information about some parts of the job as you provided (especially the torque specs for the coil bolt, and the need to remove the relay box to the side, among others). I would imagine that the proper spec on this coil bolt is pretty important to provide solid electrical connection to the plug (to avoid misfires) and mechanical sealing (to avoid dirt and water penetration/etc.) while preventing stripping of the threads. Thank you again!

I did opt to apply a little bit of Nickel antisieze on the threads of the NGK Iridium plugs. At 65K miles, the plugs were pretty stiff to remove and I want to make sure I can take them out easily at 100K or 120K for new plug installation.

[Patrick Wong]

Originally Posted by TucsonPrius

In a couple of places I read that the anti-seize can drip down onto the plug and cause mis-firing. I also know quite a number of people recommend it, too. I just don't know, for sure. Since Toyota didn't say to use it (in either the manual or the commercial brochure they provide at mytoyota.com) I went without.

Hi Shawn,

I strongly recommend use of antiseize lube, especially for modern extended-service-interval iridium spark plugs. It is only necessary to put a small dab of lube on the threads, being careful not to foul the spark plug tip.

Originally Posted by jreed

... I bought the Prius 2001-2008 Haynes manual last week and (though it has photos of a couple steps), it doesn't contain as much information about some parts of the job as you provided (especially the torque specs for the coil bolt, and the need to remove the relay box to the side, among others). I would imagine that the proper spec on this coil bolt is pretty important to provide solid electrical connection to the plug (to avoid misfires) and mechanical sealing (to avoid dirt and water penetration/etc.) while preventing stripping of the threads...
I did opt to apply a little bit of Nickel antisieze on the threads of the NGK Iridium plugs. At 65K miles, the plugs were pretty stiff to remove and I want to make sure I can take them out easily at 100K or 120K for new plug installation.

Another reason not to buy the Haynes repair manual...

The igniter wire harness connector includes a ground wire connection. However the mechanical sealing aspect remains important. It is a really good idea for you to apply antiseize, I did that at 30K miles on my 2004.

Another good reason to remove and inspect the spark plugs (even if you decide not to replace them) is so that you can inspect the condition of the igniters and make sure that no water has accumulated in the spark plug wells.

[hobbit]

At the risk of a bit of a hijack, I wasn't aware that Haynes had
a manual out for the Prius yet and went to take a look at the site.
The sample pages show that they've bought into some wrong thinking
about the car, and are now spreading that out to paying customers.
Specifically, they're claiming that a safety practice is to keep
the smartkey "at least 20 feet away from the vehicle".
.
ARGH.
.
Where the key sits is not the issue. To be safest, obviously, one
should DISABLE the smartkey using the button under the dash, and
they don't mention that. But some other cars with similar systems
don't even have a disable button, so it comes down to a matter of
PROCEDURE. If someone else is intent on powering up the car when a
colleague is working on it, keeping the key some arbitrary distance
away isn't going to matter and isn't going to be any different from
a safety standpoint than the traditional "leave it on the dashboard"
approach taken by many repair shops. It's a question of education
that another tech does NOT come up to the car and whack the POWER
button when they have no idea what the situation may be.
.
I can't believe Haynes is promulgating this crap. They should
know better.
.
I'll be they never even get into the right way to idle the engine
for vacuum-leak or other testing, either.
.
_H*

[N3FOL]

At 40K, your plugs did not really needed to be replaced. But for your peace of mind, I say you did a good job. Well done.

[philmcneal]

yeah the haynes manual is sketchy at best, if toyota had a prius offical guide book i'd buy it for sure, i can't trust 3rd party ever again...

except for hobbit hey when doing your front brakes can you get away with changing the pads if you don't remove the abs actuator relays? or is that step recommeneded in toyota's guide?

[Patrick Wong]

Originally Posted by philmcneal

yeah the haynes manual is sketchy at best, if toyota had a prius offical guide book i'd buy it for sure, i can't trust 3rd party ever again...

except for hobbit hey when doing your front brakes can you get away with changing the pads if you don't remove the abs actuator relays? or is that step recommeneded in toyota's guide?

Hi Phil,

Not sure what you mean by a "guide book". Toyota has official Prius service documentation that you can buy or download for a subscription fee: techinfo.toyota.com

Regarding your question about replacing the front brake pads, there is no need to remove the relays if you wait at least 2 minutes after IG-OFF. That step is necessary only if you are bleeding the brakes while following Toyota's procedure. See attached file.