Suddenly, oil is fouling cylinder 1 plug - cats too?

[AP9]

I don't really have time or space to tear the upper engine apart again just to experiment around, so hopefully you folks who are smarter than me can advise.

Back in March I ran some Seafoam through the intake manifold. Then one day in April while driving on the highway I felt it start to misfire, but thought/hoped I might have been imagining it or just driving on rough road. The day after I was on a longer drive on a stretch of highway (about an hour and a half each way), and halfway to my destination I started feeling it again. Several minutes later I sure enough got the flashing CEL and pulled a P0301, and watched my fuel economy tank (something like 14 mpg at steady 70 mph). Had to fill up -- no change after a new tank of mid-grade, it just misfired all the way home. Removed spark plug #1 and found it completely saturated in oily sludge and a little bit of hard deposits -- cleaned it and reinstalled. Since then, I've had similar situation happen twice, about 800-1000 miles apart. Also threw the occasional P0401 a couple times.

The engine, which never burned any oil in the first 212,000 miles of its life, is now consuming oil at about 1 quart every 200 miles. The exhaust is now slightly smoky (not blatantly so) and always smells like raw exhaust, whereas it only used to smell upon startup during very cold weather. As far as I can tell, there are no visible leaks except for minor front & rear main seals (which haven't gotten noticeably worse over the past 5 years). PCV valve and air filter are good; no evidence of any vacuum leaks. Fuel economy is good except when misfiring. No unusual engine noises except the "usual" valve lifter noise.

I'm suspecting the Seafoam either blew out a valve seal on cylinder #1 (is that even possible?) or caused a stuck ring. Does it sound like the catalytic converters are shot (though I'm not throwing a P0420 or other codes), or will I have to fix the other problem first to know for sure?

 

[derfderf]

Did you pull the plug right after the misfiring to find it oil fouled?
Had you tried pulling the plug while the misfiring was active AND before the massive oil consumption began? Was it oil fouled?

Have you checked the rest of the plugs? I wouldn't expect them to be soaked like #1, but they may yield other clues based on their appearance.

I'm a little surprised that an engine consuming THAT much oil, presumably through 1 cylinder, would run without constantly misfiring. But you indicate it does.
Which you indicate it does. And I believe you.

So it sounds like it started as an intermittent condition where oil wold suddenly gush into the cylinder, then stop. Maybe a slightly stuck open exhaust valve with an iffy valve guide seal? This condition would of course lead to significant amounts oof oil PLUS raw unburned fuel getting passed to the cat, And no compression in the cyl So a fouled plug + no compression. Not gonna fire

Once the valve unstuck itself, compression was restored and when you cleaned the plug off, so was the ability to ignite the air/fuel mixture, Cylinder operates "normally".

Maybe the sticking valve is now a burnt exhaust valve which holds marginal compression but loses oil constantly, and when it does fire, it's still losing oil.

Seems like a compression test and leakdown test are in order to find out how all that oil is getting into the cyl/.
Pay particular attention to how quickly the compression takes to max out (will likely need a helper..

No oil in coolant or vise versa, ya?

 

[AP9]

Thanks for the reply. Whether I've pulled the plug 15 minutes after shutdown or 2 days after, it would still appear oily with hard deposits underneath.

Today I pulled the plugs in hopes of doing a compression test, but my Harbor Freight Tools compression tester of course only included fittings that wouldn't start threading into the deeply recessed spark plug holes. #1 was wet with oil and had deposits again (hasn't been misfiring), but not as bad.

The other 5 spark plugs looked perfect. There is no oil in the coolant. Doesn't appear to be any coolant in oil either.

I have been throwing P0401 more frequently. Averaged 23.4 mpg last night on a 40 mile drive holding a mostly-steady 55 mph - I'm assuming all the oil being burned is triggering cyl 1 to run lean.

This rubber thing (grommet? gasket?) was lodged between the DPFE tubes and valve cover near cylinder 5. No idea where it came from:

 

[shucker1]

I'm gonna bet you stuck a ring.

Valve guides would not leak that much.

 

[AP9]

Cylinder 1: 155 psi after 5 cranks (137 psi after 3 cranks) - oil present in cylinder after cranking
Cylinder 2: 145 psi
Cylinder 3: 155 psi
Cylinder 4: 145 psi
Cylinder 5: 155 psi
Cylinder 6: 155 psi

 

[shucker1]

For 212,000 miles that's not bad readings except for #1. If it drops that much after 3 cranks something is going on in that hole.

Leak down test would be next.

This might explain it better.

http://www.hotrod.com/articles/cylinder-leakdown-tester/