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Old 02-27-2017, 01:37 AM   #1
Vancouver98STi
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1998 JDM Impreza STi
V4 GF8 White

Exclamation One oily spark plug

I pulled the spark plugs today on the EJ20K engine in this '98 Impreza STi that I've had for a couple months. First time I've ever pulled the plugs on a Subaru engine. Wasn't too bad with the battery and air filter box removed.

I suspect these NGK spark plugs (BKR6EIX-P) have been in this engine for a long time. Car has 140,000 km on it. I was a little disappointed to discover that the spark plug from cylinder #4 was rather oily. The sheen is quite noticeable on the ground electrode and on the nose of its ceramic insulator in the image below. I'm hoping this isn't an indication that major engine issues are imminent (or have already occurred).




I want to replace these with regular BKR6E spark plugs. I see that NGK has a slightly different version of this plug, BKR6EYA which is supposed to be "fouling resistant". I thought maybe this might be worthwhile to try, keeping in mind that one cylinder seems to have an oil problem. Anyone have any thoughts on this? Any reason why using a "YA" plug (fouling resistant) would be a bad idea?
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Last edited by Vancouver98STi; 10-25-2020 at 03:08 AM. Reason: Replaced missing image
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Old 02-27-2017, 09:26 AM   #2
Charlie-III
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I would stick with what you currently have in terms of type. Put in a new set and get 5-10k miles on them and pull to recheck.
Your current plugs may just be high miles and not dealing with a higher mileage engine well.
If you change plug type, it's harder to compare them to what you currently have.
If you're not,blowing a lot of blue smoke out the exhaust, I wouldn't worry about swapping plugs for a different type.

In general, mixture looks a little rich.
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Old 02-27-2017, 05:03 PM   #3
Vancouver98STi
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V4 GF8 White

Lightbulb I have very limited experience with this car...

Quote:
Originally Posted by Charlie-III View Post

If you're not blowing a lot of blue smoke out the exhaust, I wouldn't worry about swapping plugs for a different type.
I've not seen any evidence of blue smoke, but... I've only seen this engine run twice... the day I first looked at this car, and the day I drove it home. Well okay, I've had the engine running a couple of times in my driveway... but other than that the car has been uninsured and parked in my backyard the last couple of months as weather permitting (between rain and snow storms) I've been doing little things to it here and there.

Quote:
Originally Posted by Charlie-III View Post

If you change plug type, it's harder to compare them to what you currently have.
I'm still curious to hear from anyone though if there'd be any detrimental effect to running YA (fouling resistant) spark plugs in this engine. I'm totally new to turbocharged engines, so I'm just sort of wondering if the slightly more projected tip of the YA plugs might possibly cause any (detonation?) issues while under boost.


Last edited by Vancouver98STi; 10-25-2020 at 03:10 AM. Reason: Replaced missing image
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Old 12-13-2017, 08:59 PM   #4
Vancouver98STi
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V4 GF8 White

Thumbs up

An update on this thread...

I ended up reusing the BKR6EIX-P plugs (with new BKR6E spark plugs on reserve) just to see how well the engine would continue to run... and it's been fine.

The reason for the update is that I also installed two custom made oil catch cans (discussed Here and more Here), which seem to be working well... and the #4 spark plug no longer has an oily sheen to it. Coincidence? I dunno... but I'm pleased.
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Old 12-14-2017, 02:59 AM   #5
ForesterinRHD
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Old 12-19-2017, 08:27 PM   #6
wtdash
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Good news :-)
Ensure you check your oil level EVERY fuel (petrol in BC?) fill-up. If it's burning oil you don't want to wait 'til it runs low. If that oil light ever comes on it's usually too late.
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Old 12-20-2017, 02:37 AM   #7
Vancouver98STi
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1998 JDM Impreza STi
V4 GF8 White

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Quote:
Originally Posted by wtdash View Post

Ensure you check your oil level EVERY fuel (petrol in BC?) fill-up.
The most commonly used term in BC (along with the rest of North America) is gas. It is never referred to as "petrol" here... except maybe by expats from the UK.

Deserved or not, the EJ20K has a reputation of being a ticking time-bomb... so yeah, I keep a pretty close eye on maintenance with this engine.
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