Compression test - high result in cylinder 4

Hi All,
Haven't been about in a while but running a CRV - ictdi (09) now.

I serviced the car about 3 weeks ago and found an oil mist in the air filter box, there's also been a minor rattle at mid load on occasion that I though to be a fuel issue. I found what is a minor oil leak at the back of the engine too. Its been there a while and the source is not obvious. The car is not using oil excessively at all and there are no tell tale oil drops on the driveway either.... very confusing.

The oil in the air filter box can only come from a turbo seal or more likely from the rocker breather. The car is running reasonably well though with no smoke issues or noticeable power deficiency.

When the engine is running, there does seem to be a bit more pressure than I'd have expected when you take the oil cap off. This lead me to think that I have a blow by issue, hence the compression test. With the compression ratio being ~16:1, I was expecting a good result to be 15-17 bar. These are the results however (all dry test);

cyl 1; 17 bar / 225 psi
cyl 2; 17 bar / 225 psi
cyl 3; 16 bar / 220 psi
cyl 4; 22.5 bar / 265 psi

Cylinder 4 has me stumped, any ideas folks?

JM

Hi,

Dry compression test looks good did you try to run again and also try wet test ?

Hi,
Yes, I ran the test again and this time greased the threads of the glow plug adapter just in case. Just as well too.
340/330/315/340 psi.
So a little low on cylinder 3.

Personally I would say that difference isn’t so significant. Is the only issue some oil residue in the air box? Are you sure you haven’t overfilled the oil on one occasion?

No didn't overfill, always carefull about that. Considering the slow leak at the back of the engine somewhere and what seems to be slightly higher blow by at the oil filler cap than I've had with previous engines in the Civic and Accord, I think there's a crankcase pressure issue. Have you come across much of this in your travels?

Nope never.