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Old 07-03-2009, 04:23 PM   #8 (permalink)
Christ
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Join Date: Nov 2008
Location: Troy, Pa.
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Pasta - '96 Volkswagen Passat TDi
90 day: 45.22 mpg (US)
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Quote:
Originally Posted by Cd View Post
Whuups !
I meant "blow-by ".

The spark plug has a large amount of oil on the threads when I remove it, yet the spark plug wire boot is spotless. ( Also the tubes are clean on the sides .)
I don't understand where that the oil is coming from.
Also, I don't understand how that oil could seep into the threads like that, unless it leaks downwards as remove the plug. ( The plug is screwed in very tightly.)

This sounds like the ring seal problem that you were describing.
My car is very sluggish, yet the F.E. seems normal ( around 38 MPG, with over 45 MPG on the highway on a nice long trip. This is with an automatic. )
I have been thinking that if something was wrong with the car, that the mileage would drop. I guess this is not the case.
Also, I might add that I passed my emissions test easily. If oil is getting mixed into the engine where it shouldn't be, wouldn't this cause more pollution ?

Thanks !
Blow-by is common for lack of power, but is also a cause of oil burning. If you don't have both, you don't have blow-by.

Oil on the spark plug threads would only happen as a result of blow-by if you're using an incorrect length plug. The threads are normally covered, except maybe the last 2-3 closest to the electrode.

The only way that oil will get on the threads is while you're pulling the plugs out, and then only if there's a leak in the lower tube seal.

Oil on the boot itself indicates and upper seal leak, no oil on the boot, or only on the tip of the boot, indicates a lower seal leak. It's not to worry about, honestly.

As for your lack of acceleration power, do a compression test first of all. The tester is only about $20, and it's the first diagnosis tool besides a vacuum gauge that most people will need.
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