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Discussion Starter #1
These are two of the 6 spark plugs I just took out from my 02 Sienna. These plugs (Denso SK20R11) are <3000 miles old (or say young?)

What can you tell, for the engine, by looking at them in the pictures?

Thanks.

IMG_1955.jpg IMG_1956.jpg
 

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Discussion Starter #4
Looks like oil fouling. Ever fix the OCV?

I attached a photo of my latest plugs, after about 70,000 miles on them...
Thanks, I have't ordered the new OCVs yet but will do very soon. I am thinking to do a compression test (dry and wet) so I pulled all plugs out. Not sure if due to engine running rich or burning oil. My van is burning oil on a surprising level. It burns even more oil after I replaced the oil pump. I am not sure if it is due to the higher oil pressure, yes, the oil pressure increased a lot after the oil pump replacement.

BYW, I replaced all the spark plugs last year when I did the TB and oil pump job. The previous set of plugs I took out (over 50k miles) looks lot better than the current one. Why?

For the compression test I think I can only do a "cold" one. But as I read from web that people say a cold engine compression test is not accurate so you have to do a "warm" test. But my current situation probably doesn't allow me to do a warm test. Will a cold test show something? I would like to know if oil burning is due to a ring or valve seal.

Thanks
 

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Did all the spark plugs look like that? In other words, was this an engine-wide problem?

Also, I don't remember whether you had ever replaced your Air/Fuel ratio sensors (A/F sensors). These sensors should generate a P1135/1155 when bad; they control the lean/rich fuel trim. Many Sienna owners, including me, had both sensors go bad around 100-125,000 miles.

Your engine's possible sludging history makes your situation more difficult, though, and you might have more than one, and more atypical, problems. It's also possible that if you're burning oil, the A/F sensors might be fouled, causing the rich running.
 

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Discussion Starter #6
Those two plugs in the picture are the worst and others are a little better. Also I can see the #1, #3 and #5 plugs are a little better then #2, #4 and #6. They are just black color like carbon but not oily. Just a little bit oil on the first two threads. I have never got P1135/P1155 and never changed them, but I will test them. Here is a picture of 3 of the previous plugs, they are >50K miles. IMG_1957.jpg
 
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