#1 plug oil-fouled & can't find the source.

[syty1]

I noticed a low speed miss leaving the office, & checked the plugs when I got home:




(click the image to expand)

#1 was oil-fouled severely & the rest were clean. The #3 head cover was replaced w/ drain plug gaskets & the gallery is dry - no oil on exposed part of plug nor the threads.
Changing out the plug,the wire and the coil made no difference.
Leak-down test: all cylinders 22 or 23% (cold) & compression test: all 150 or 175 (#1 = 150) (warm)
The valve seals seemed the most likely suspect given that the rings seem good so they were all replaced w/ Vitons over the weekend.
NO difference.

This engine was rebuilt summer before last (leaking head gasket) w/ mirror finish head & block Cometic MHG, ARP studs torqued to 85 ft-lb & new rings on the stock pistons. The bores were pristine & still showed the original hone pattern @ 90K....pistons well w/i TRSM spec's & reused. Bores were litely honed for the new rings, and they were individually gap-checked in their bores.
All new seals, gaskets, etc.
Still running the original CT 26, & it is leaking some oil on the intake side. I have a 57 trim on the bench I want to use - but I'd like to solve this 1st.
There are no mods to the PCV system, the TB orifice is not obstructed, the original intake system is still in place & unmodified except the Porsche BOV. I fabbed a 3" exhaust to the cat & cat-back is HKS 65mm.

AFR's 11.5 under boost.

So, now I'm scratching my (anatomy)... Do any of the 7M gurus have any ideas? The only oil leak I can find is the turbo, but all the oil can't go to only one cylinder??
Open to ideas over here.....

 

[hvyman]

Sounds like rings. If 1 was 150 and the rest 170 that's a bit of a difference. Did you try adding a little oil to no 1 and re doing the compression test to see if it went up?

 

[Poodles]

Overtightened timing belt tensioner bolt could be the culprit...

 

[hvyman]

Which leads to an oval cylinder no 1.

 

[IJ.]

Overtightened timing belt tensioner bolt could be the culprit...

This..

 

[syty1]

LOL @ Poodles!

HVYMAN - thanks for the reminder...comp was 150 in 3 cylinders & 175 in the others; so not isolated low in #1.

IJ.....I'll take pix (sigh)

 

[3p141592654]

Does overtightened mean greater than the recommended 36ft-lbs, or is it a problem even using the recommended torque?

 

[syty1]

Damn! No wonder I'm in trouble here - I thought it was 39 ft-lb...!

 

[IJ.]

Does overtightened mean greater than the recommended 36ft-lbs, or is it a problem even using the recommended torque?

Measured half a thou deflection at 36ft/lbs...

I always had my blocks bored and honed with the Tensioner in place after the above fail.

 

[syty1]

Well, pulled the engine & #1 piston. Everyone was wrong (me included).
Pix coming...

 

[maxburn]

What was the issue?

 

[syty1]

This is what I found upon pulling the #1 piston.

I was meticulous in orienting the end-gaps properly & double-checking each piston as I loaded it into the ring compressor for installation.
I've never seen this happen before...I know the rings can migrate some initially. But how does this occur?
I J your thoughts?? Have you seen this before?

 

[IJ.]

This is what I found upon pulling the #1 piston.

I was meticulous in orienting the end-gaps properly & double-checking each piston as I loaded it into the ring compressor for installation.
I've never seen this happen before...I know the rings can migrate some initially. But how does this occur?
I J your thoughts?? Have you seen this before?

I'd be digging some more, scrapers lined up shouldn't have been that much of an issue, what were the end gaps of everything on assembly?

What was the piston to bore clearance?

Have you micced up the bore where the tensioner bolts on?

 

[syty1]

OK, mic'ed up the #1 cylinder:
Top ring end gap - 0.559 mm
2nd ring - 0.584 mm
oil ring - 1.143 mm (oil rings have little tension against the bore)

bore thrust side
top 3.2695"
mid 3.2680
bottom 3.2685

bore pin axis
top 3.2680
mid 3.2690
bottom 3.26855

bore @ tensioner level 3.2685" @ 36ft# torque & 3.2680 loose

Piston mic'ed @ 3.2660 for an oil clearance of 0.0020"

These all seem to be within specs - the ring end-gaps list from 2009 assembly I cannot find, but the cylinders are unbored & the pistons are original. The bores were deglazed by the machinist who decked the block 0.005 for the MHG.

I do live in the mountains, and have about 7 miles of downhill engine braking at 60mph or so every day, & 4.5 miles downhill in the opposite direction. Perhaps that is enough to oil things w/ the end-gaps aligned?
I replaced the valve seals w/ new vitons a couple weeks ago with no improvement; so I think that's eliminated, too...
Anything else I should check??

 

[super51fan]

How about this theory. You had a misfire caused by bad wire or coil. The now firing plug of course shows oil on plug due to non firing of plug. A non firing cylinder usually has low compression due to fuel washing down cylinders. Maybe instead of a tear down you need to fix a misfire caused by bad wire or coil or coil connector problem. When you go back together make sure your rings are not upside down. Replace plug wires and swap coils on bracket. Good luck. Even if your wires are newer I would buy new OEM wires and plugs. Good luck.

 

[syty1]

I replaced the coil, the wire & the injector as stated in the 1st post.....with no improvement.
Had the same thoughts...

 

[super51fan]

Sorry I missed that. How long for the new plug to get fouled? How about a pic of the intake ports. I don't see piston and cylinder the problem if you measurements are correct. You are sure the rings are not on upside down.

Hey did you also install a new plug when changing the plug wire. A fouled plug will not fire even if you correct the cause of the misfire. The deposits become a conductor.

 

[syty1]

Good thoughts. I went down the same path. The plug would be wet when checked after about 15 miles round trip to my office; but still firing well & engine was strong.
Switching #1 & #6 plugs resulted in the new #1 fouling & the new #1 being clean. Since they run off the same coil, 6 was chosen intentionally. I still changed out the coil hoping that would be "it"...

The top ring has a mark to indicate the side facing up - correct orientation confirmed.

I would think anything dumping oil into the intake system would affect more than one cylinder (except valve seals which were replaced).

I'm not finding any source except the oil rings...the end-gap is on the wide end of spec's and they were aligned as seen in the photos. Also, the pressure against the cylinder wall seems weak. I've only pulled #1 so far - I'll pull the rest this evening & compare.

 

[super51fan]

I was thinking that maybe loose, not installed all the way down and came off of guide. Maybe spring knocked off valve stem seal just on #1 cylinder.

 

[syty1]

I'll check the valve stem seals to make sure they're properly seated.

I am finding an oil-film from the accordion tube thru the 3k pipe which I attributed to the PCV system. I checked the TB orifice early in the investigation & again last nite & it's not restricted, nor is the PCV tube/hose...