987.2 9A1 engine bore scoring assesement

[hyperboleap]

I have a 2009 987.2 Boxster S 3.4 (9A1 engine, PDK) at 120k miles. Noticing dry black carbon fouling on brand new plugs after ~500 miles.

Borescoped all six cylinders through the plug holes.

Bank 2 (cylinders 4-6) looks clean - no marks visible. Bank 1 (cylinders 1-3) shows some vertical marks that initially concerned me, though they don't look like the deep tramline scoring I've seen in severe examples online. Also, some dark staining.



Looking for experienced eyes on whether these marks look like active bore scoring, or something else?


These are on one cylinder of Bank 1, I think cylinder 2. Another cylinder on this bank has similar marks, but not as severe.








Plugs bank1








Plugs bank2








Videos

Bank 1

https://www.dropbox.com/scl/fi/tqmomb0hzuqd0u5vxmh...


Bank2

https://www.dropbox.com/scl/fi/8gkhp4dj8x90ypiflek...


Many thanks in adavcne!

[Slippydiff]

I'd be tempted to do a leakdown test to make sure there's nothing obvious wrong mechanically.

It looks quite wet/oily in there, which makes me wonder if the rings are gummed up or the valve stem seals are past their best. The result of which could be higher than normal levels of carbon build up, which in turn have come adrift from the piston crown/combustion chamber in the head and then got stuck between the piston and the bore and created the marks you're seeing. In which case they're not bore scoring as such, more it's very light abrasion.

[hyperboleap]

Thanks, will do leak down test next.
AOS was knackered when I got the car. The intakes and air filter housing were full of oil. I replaced the AOS 700 miles ago and cleaned as much as I could, but I wonder if there is still some oil residue getting into the cylinders, or do you think 700 miles is enough to burn that off?

Edited by hyperboleap on Friday 6th March 16:48

[Slippydiff]

hyperboleap said:

Thanks, will do leak down test next.
AOS was knackered when I got the car. The intakes and air filter housing were full of oil. I replaced the AOS 700 miles ago and cleaned as much as I could, but I wonder if there is still some oil residue getting into the cylinders, or do you think 700 miles is enough to burn that off?

I'd have thought 700 miles would have been sufficient, but that's dependent on driving style.

I wonder if there was so much oil in the cylinders, it's gunned up the oil control rings.

I imagine there's a product in the form of a fuel additive that might clean the rings over time.

[Ed.Neumann]

Like slippy says, I would consider a decent engine flush that aims to break down carbon deposits that can gunk up your piston rings.

Then when you put new oil in maybe consider adding some Liqui Moly Motor Oil Saver, this has really good results for swelling seals, valve stem seals in your case.

Then keep an eye on it, see if it gets better.

I wouldn't be concerned about those marks, that looks pretty normal.


What fuel are you using?

[Clad-Hach]

These seem to be dirty engines, I think those plugs look fine for a direct injection engine my Kia Proceed GT looked the same, the exhaust tips on my 987.2 CS are always dirty black as was the Kia, perhaps its a trait of these type of engines without PPF/GPF filters.

How do the inlet ports look, have they furred up from carbon deposits, at 120k miles it might be worth checking.

Do the tried and tested valve stem seal check getting someone to follow you is best.

A fast steep down hill road get the revs up then lift the throttle for a good few seconds then floor it, if blue smoke is seen its the seals.

A worn engine would burn oil all the time and you would see it.