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2005 Corolla Ce 29k Miles, Spark Plug Replacement Question


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#1 Rene Resendez

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Posted 10 January 2008 - 11:37 AM

OK, I hope this does not make me look stupid, but my 2005 Corolla will soon hit 30K miles, the manual say don't replace the spark plugs until sometime after 90K miles, but I recently purchased a Haynes repair manual that states the spark plugs should be replaced every 30K miles. Who is correct? Haynes or the Toyota manual!!!

Thanks in adavance to anyone who give me a good answer.

#2 fishexpo101

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Posted 10 January 2008 - 11:50 AM

Welcome to the forums. Your Corolla comes with long life Iridium plugs from the manufacturer. They are supposed to good for as long as 120K miles before they need to be replaced. Might not be a bad idea to take them out at 30K-60K mile intervals to at least visually inspect the plugs. Also help keep them from freezing (corrosion) to the aluminum head. On my Corolla - I changed my plugs between 90K-100K miles and they still looked pretty good. I changed the Matrix ones at 60K - just to be on the safe side. Same way with those, plugs looked perfectly fine - so I'll just keep them as spares.

I do not believe that I've ever seen a Haynes manual for a 9th generation Corolla - last one I saw was one for 1993-2002 (7th and 8th generation Corollas). Maybe it just came out recently - but chances are they were referring to standard copper plugs, with generally need to be replaced every 15K-30K miles. When it comes down to replacing your plugs - high recommended to stick with OEM type Iridiums - some have had very bad luck using other types of plugs. Some have experienced issues from burned out coil on plug units to damaged piston and/or cylinder walls from a broken ground electrode.

#3 Bikeman982

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Posted 11 January 2008 - 02:59 AM

Some manuals (including Haynes) have inaccuracies printed in them.
They try to use the same information as past manuals to save printing costs, but they may not be right.
I would do as Fishexpo101 recommends and take them out and inspect them.
Check the appearance and also the gap on them.
Note what kind they are and check up on their life expectancy.
Different types of plugs have different longevity.
Hope this helps.

#4 Larry Roll

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Posted 11 January 2008 - 10:58 AM

There is a new Haynes manual for the 9th generation Corollas, I recently saw it at Pep Boys or Auto Zone or someplace like that. I didn't buy it.

I have two questions with regard to checking/replacing spark plugs on a 9th gen. Corolla.

1. How do you remove the plastic cover over the engine? I've never done it. The fasteners that are on the corners of the plastic don't react to being manipulated by screwdrivers or pliers, unless a destructive amount of force would be applied. I can't move them. How do they work? I have the CD manual, but it does not address this issue. I need to know the direction they move for removal and replacement, how much force is necessary to move them, and what kind of tool is required. Is this cover necessary to the operation of the engine, or can it be deleted without any ill effects?

2. What is the spark plug gap? How do you gap an Iridium plug? I have no experience with them, and need the Iridium Plug 101. Please explain this to me as if I just came off the space ship from the planet Zlork, where we never heard of Iridium plugs.

Edited by Larry Roll, 11 January 2008 - 11:00 AM.

#5 fishexpo101

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Posted 11 January 2008 - 12:56 PM

Good to know - I didn't know the 9th gen Haynes manual came out.

As for the engine cover garnish - there are two 10mm nuts that are easily removed closest to the front of the cover. The two rearmost ones are the plastic "brush" pins - there should be a flattened portion on the top that looks like they can be manipulated by needle-nose pliers. Just turn them CCW as you slowly try and pull on them - they will come out. Even if you are careful - there is a chance that they will break, I broke both of mine on my 2002 Corolla. No big deal - the engive cover will be well supported by the two nuts up front - of you can run without the engine garnish.

Once that is off - you will be able to see the C.O.P. (Coil on Plug) units sitting right ontop of the plugs. There is a 10mm bolt that holds the C.O.P. to the valvecover and an associated electrical connection as well. Just undo the clips (there is a tab you have to depress first), might help to use a flat bladed screwdriver to pry the clips off - undo the 10mm bolt, tug on the C.O.P. and it should pull out to reveal the plug in the sparkplug well. Use the appropriate sparkplug socket and enough extensions - to loosen the plug.

The sparkplug gap is the distance between the ground electrode (ground strap) and the anode of the plug. Most Iridium plugs come pre-gapped from the manufacturer and protected by a cardboard tube to prevent potential damage from shipping/handling. Though it is still good practice to verify the gap of the plug before it goes into the engine. Word of warning - Iridiums and platinum plugs do not take kindly to improper gapping techniques - this is the leading cause of physical plug failures. Good example are the Bosch+4 plugs - with four ground electrodes - uses a special gapping tool. Regular gapping tools cannot measure the gap correctly, and too much flexing of the ground electrodes tend to cause them to shear off inside the combustion chamber causing significant damage. Iridium is a very hard material, but the anode can similarly be damaged if you do not gap the plug correctly.

#6 Larry Roll

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Posted 13 January 2008 - 10:29 AM

Fish:

Excellent reply, thanks. I will keep this info secure until I get around to checking my plugs. Since I'm not experiencing any problems with them now, I'll follow the advice of "if it works, don't fix it." I've tried a few times to remove those brush clips, but couldn't figure out how they wanted to be manipulated to get them out without breaking them. I guess that that's not even possible, but it's good to know that the 10mm nuts will hold the garnish sufficiently. I just hope there aren't any rattles.

#7 Bikeman982

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Posted 14 January 2008 - 02:56 AM

"If it aint broke - don't fix it". Good philosophy.
I have often times broken parts because I was curious and wanted to know how they were put together.
Now I do most of my experimentation at the local junkyard which is full of test subjects.

#8 doubletrouble

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Posted 15 January 2008 - 08:40 AM

my sienna started missing at about 120000 . i think the plugs were changed at 60. thats what my mechanic best friend says. he sees misfires on iridium plugs between 60-90000. also ,on toyota use ONLY original equipment plugs. either denso or n.g.k. just trust me on this one. pay the extra money and buy them ahead off ebay or drivewire.com. half the price of the dealer or local stores. My $12 plugs were $6.50 shipped .

#9 jimb29635

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Posted 28 February 2008 - 10:00 PM

Those iridium plugs are supposed to go 100K miles. I've read to remove and reinstall them at 50k miles so they don't fuse to the engine block.

#10 BobLevine

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Posted 29 February 2008 - 03:38 AM

Those iridium plugs are supposed to go 100K miles. I've read to remove and reinstall them at 50k miles so they don't fuse to the engine block.


Dealer did mine and the plastic pins broke off.

I'm anal since I paid them $120 to change the plugs and had the broken plastic removed and new pins put in.

As fish said, the pins are cosmetic, but for $120 it should be done perfectly.