Pulled plugs, 1 is oil fouled

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olyfiveoh

New Member

Dec 27, 2004

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Jan 19, 2009

#1

• Jan 19, 2009

• #1

I have a 90 GT that is for the most part stock except for an o/r xpipe, and mac induction tube. I recently saw my fuel economy drop way off and did a tune up.....oil, plugs, air filter. One of my plugs was a bit fouled and so i checked the new one after 200 miles of driving. the new plug was extremely oil fouled and looked as though it was not even firing. This obviously leads me to believe that there is an oil leak into that cylinder, however, my car is not smoking at all and does not appear to be losing much oil either (it always burned a little). when driving, the car seems to be firing all 8 cylinders and the power seems normal. My MPG went from around 17-19 to 12-14. Any ideas on what the cause could be?

 

white 89 GT

Member

Apr 3, 2003

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Tacoma

Jan 19, 2009

#2

• Jan 19, 2009

• #2

Was the plug # 4 or # 8 that was fouled.

 

dcurtis

10 Year Member

Jan 19, 2006

688

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Jan 19, 2009

#3

• Jan 19, 2009

• #3

The pcv valve could be sucking the oil into the intake and fouling the plug most of the time the 4 and 8 plugs.

 

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olyfiveoh

New Member

Dec 27, 2004

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Jan 20, 2009

#4

• Jan 20, 2009

• #4

it was plug 8. can i test the pcv valve?

 

squeak93

15 Year Member

Jun 2, 2005

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Joplin, Missouri

Jan 20, 2009

#5

• Jan 20, 2009

• #5

Its like 4 bucks if that, just replace it, clean or replace the plug and let us know.

 

white 89 GT

Member

Apr 3, 2003

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Tacoma

Jan 20, 2009

#6

• Jan 20, 2009

• #6

If after you change the pcv valve and it still fouls out, (I think it will) pull off the drivers side valve cover and see if the oil return hole is partially pluged. You see the engine slopes toward the back and if oil is slow at draining down the hole in the end of the head it will drain down the first valve guide it comes too.#8
So make sure the oil drain hole is not plugged, use coat hanger etc. to make sure.

 

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olyfiveoh

New Member

Dec 27, 2004

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Jun 15, 2009

#7

• Jun 15, 2009

• #7

So i know this is an old post but I had my car put away for a while. i changed the PCV and the bad plug and then put it away until the summer. i just drove it up from storage which is about a three hour drive and after checking the plug, it is fouled again, just as Whitegt predicted. Are there oil return holes on each head, or just the drivers side? Will it be pretty obvious where it is when i pull the valve cover? pictures anyone?

 

Strype

Cuthbert catcher

Founding Member

May 11, 1999

61

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Huntsvegas, AL

Jun 15, 2009

#8

• Jun 15, 2009

• #8

olyfiveoh said:

So i know this is an old post but I had my car put away for a while. i changed the PCV and the bad plug and then put it away until the summer. i just drove it up from storage which is about a three hour drive and after checking the plug, it is fouled again, just as Whitegt predicted. Are there oil return holes on each head, or just the drivers side? Will it be pretty obvious where it is when i pull the valve cover? pictures anyone?

Click to expand...

Little holes on the front and back ends of both heads.

 

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NotchAbove

New Member

Jan 24, 2007

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Jun 15, 2009

#9

• Jun 15, 2009

• #9

Not to be the bearer of bad news, but to me this sounds like a valve seal. Basically when the car sits, the oil leaks down into the cylinder. Fouling the plug. When the car is running there is not a substantial amount of oil dripping down, so you will not see it burning.

Another possibility that I am very familiar with is a lower intake gasket leak. If you have a lower gasket leak the cylinder will pull oil from the lifter valley into the cylinder and foul the plug. However you will be able to identify that by opening the oil filler cap and see if there is any change in vacuum.

 

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PJC Racing

New Member

Nov 21, 2007

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Jun 15, 2009

#10

• Jun 15, 2009

• #10

Valve seals.