MIsfire in #3

[maui_beetle]

I have a 2000 1.8t NB with 143K miles. It is having misfire problems in cylinder#3. It seems Oil is leaking onto the plug on the combustion chamber end. So far I have covered the basics:several new coils, new plugs, changed the valve cover gaskets, and re-taped my coil wire harness. When I pull the new plug out the thread and electrode are coated in oil. No other signs of wear or soot on the plug. The car runs fine, no loss in boost or any noticeable problems while driving. CEL codes are 16684 and 16687.

Also, I have an oil light that comes on often when the car is stopped at a light. I've had the oil pressure tested as well as the oil pump by a good VW shop with no problems. Also, I cleaned the pick-up tube really well when I changed my oil pan. I'm running Mobil 1 5w-30 synthetic every 3000 miles and a good Bosch filter.

Could the 2 problems be related? A knowledgeable friend with the same NB suggested that it might be the a leak in the valve stem seal. I've scoured this site and others and have not found many answers beyond what I've already done. I need to take it to a mechanic, but I thought I'd ask for help first. Thanks for your time.

[wawalker]

Well, there are basically 2 ways for oil to get on the plug in the combustion chamber: a) past the piston rings (which at 143k miles isn't surprising) or, b) leaking valve stem seals.

Some oil, especially at that mileage is prolly pretty normal and on a 1.8t the turbo is also a potential source, but it would be in all cylinders. Your codes are random misfire and #3 misfire detected in case someone else reads this.

Since you've had the pickup and pump checked you might try a new pressure sensor and/or if this is only happening when it's all warmed up try moving up to a 5W-40 or 10W-40 oil for a little more viscosity when hot.

Are you actually on Maui? If so, I am uber-jealous--been there 2x and it's very hard to leave. Also, how did you get so many miles on it on an island? Do you drive from Lahaina to Hana every day?

[maui_beetle]

Thanks for your help Bill. That would confirm my latest suspicions, and beyond my abilities. I will be sure to post whatever finding I get back.

I will try switching the oil ASAP like you said.

Yeah I am from Maui. I live way up on the mountain in Kula. The car had high miles when I bought it in Portland OR a few years ago.

[wawalker]

Good luck!

[maui_beetle]

Mechanic ran a compression test and said the 3rd piston is probably toast. He recommended putting in a used engine over a full tear down. With the high mileage that I have, it sounds like the lesser of 2 very expensive choices.