spark plug replacement

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

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

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

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

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*

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.

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.

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.

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*

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.

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.

Prius spark plug gap? Anyone know?

Curt

Hi Curt,

1 to 1.1 mm is the spec. (0.039" to 0.043")
Replace when the gap grows to 1.2 mm or 0.047".

The correct iridium spark plugs are Denso SK16R11 or NGK IFR5A11.

I don't quite understand you reasoning for replacing the OEM spark plugs which are platinum tipped which should last upwards of 100k miles @ 40k miles unless you were experiencing mis-firing or something similar. The plug are difficult to remove and you are tempting fate by messing with the individual coils on top of each plug, which I sadly discovered have a high failure rate due to the excess heat under the hood.

Please explain your logic!

Thanks, Patrick!

Curt

One thing I'll add to the discussion is a short warning about the ignition coil reinstallation. When I changed the spark plugs on my last car with the same 1NZ-FE engine, I got sloppy and didn't start the bolts by hand. Steel bolt + aluminum cylinder head...what do you think happened? You guessed it - stripped out the hole something fierce. Hopefully, you'll all learn from my mistake and keep the wrench away from the bolts until you're sure the bolt is threaded properly.

The OP explained his logic very clearly in his first post?!?!

BTW The spark plugs are Iridium not platinum. The first batch of "long life" plugs developed were the Platinum plugs that were good for about 60k miles on most engines. The irridium plugs last longer and work better than the platinum tipped plugs. I read a really interesting research paper by the developers of the Iridium plugs. (Some fellows from Japan). Stated all of the design goals for their new plug. (Longer life, better spark, etc) they met all goals with the Irridium plug. They really are an engineering marvel. 100k miles with only a slight increase in the gap. Platinum are only good for about 60k miles. (still pretty amazing).

A good lesson to share. Tightening torque for that bolt is 80 in-lb.

A related suggestion is that I use a length of rubber hose as my spark plug wrench. The inner diameter of the hose is large enough to fit over the spark plug tail. The idea is to insert the spark plug into the rubber hose, put a small dab of antiseize lube on the spark plug threads, then lower the spark plug into the spark plug well using the rubber hose. Turn the hose to get the spark plug started in the spark plug hole. When the plug is finger-tight, then you can pull the hose off. If for some reason the plug starts to cross-thread, the hose will come off without causing damage to the cylinder head.

Then torque the spark plug to 13 ft.-lb.

I didn't even know the Prius had spark plugs. I figured it would use laser beams or a particle accelerator or something to ignite the gas.

Shawn was reasonably concerned about the plugs sticking in the cylinder head if left undisturbed for 120K miles. Some owners might just remove and replace the old plugs after applying antiseize lube, but he decided to replace the plugs with new while he was at it (they are not very expensive since there are only 4 to buy.)

The spark plugs are not difficult to remove compared to many other vehicles, as long as you remove the relay box mounted to the cowl to improve your access and have the appropriate length extensions for your ratchet wrench.

It sounds like you had a problem with the igniters, I would like to hear more about that and what DTC were generated. I am not aware that they are prone to problems other than being damaged due to water accumulating in the spark plug well. The Prius engine runs pretty cool compared to most vehicles.

thanks pat! i just rememberd reading that when a person opens the door it activiates the brake test system, and having my door open once when I was doing a air cabin filter change I did hear some noise related to the brake system... now I thought if my caliper was mounted like that would it fire? even after waiting 2 minutues before dissasembly?

i kno you can dl teh manuals for 10 bucks but that's such a hassle, i wouldn't mind paying for a hard cover on hand.