Hi all,

I had noticed previously that the oil consumption of my 2008 Mk2.5 1.8 Petrol was quite high. I had also noticed that when driving at high speeds on the motorway the car would hesitate and at least once I noticed the EML light flash which I learned was to indicate a misfire and sure enough when I plugged an OBD2 reader in it threw up a misfire in cylinder 2 code.

Last weekend I changed the oil and since I wasn't entirely sure of the service history of the car and the fact it had a misfire I thought I'd change the spark plugs. Cylinder 1 was fine, cylinder 2, 3 and 4 all had oil on the plugs. There wasn't oil sitting in well but the plugs were dripping wet with oil. I've changed them and it does feel like it is running slightly better but obviously this won't fix the issue. I've ordered a new rocker cover gasket as I've read that this is likely the cause of this issue but have also read that the PCV valve and the hose collapsing under pressure could also be causes. 

Is it possible for me to check the PCV hose condition without taking off the manifold as I've looked and read that it's a bit of an involved job since the PCV is buried underneath everything?

Initially after looking at cylinder 2's plug I had resigned myself to it being a piston ring issue but surely if 3 and 4 are also all oiled up then that's unlikely?

2 hours ago, Shominy said:

Hi all,

I had noticed previously that the oil consumption of my 2008 Mk2.5 1.8 Petrol was quite high. I had also noticed that when driving at high speeds on the motorway the car would hesitate and at least once I noticed the EML light flash which I learned was to indicate a misfire and sure enough when I plugged an OBD2 reader in it threw up a misfire in cylinder 2 code.

Last weekend I changed the oil and since I wasn't entirely sure of the service history of the car and the fact it had a misfire I thought I'd change the spark plugs. Cylinder 1 was fine, cylinder 2, 3 and 4 all had oil on the plugs. There wasn't oil sitting in well but the plugs were dripping wet with oil. I've changed them and it does feel like it is running slightly better but obviously this won't fix the issue. I've ordered a new rocker cover gasket as I've read that this is likely the cause of this issue but have also read that the PCV valve and the hose collapsing under pressure could also be causes. 

Is it possible for me to check the PCV hose condition without taking off the manifold as I've looked and read that it's a bit of an involved job since the PCV is buried underneath everything?

Initially after looking at cylinder 2's plug I had resigned myself to it being a piston ring issue but surely if 3 and 4 are also all oiled up then that's unlikely?

Unfortunately that engine suffers from excessive piston ring wear, especially when a previous owner hasn't kept the oil clean.  In terms of the PCV valve/hose combo, the valve getting stuck/blocked as well the hose going weak so it can collapsed can both cause major running issues.  I'm afraid the only way to get at the valve and hose is by removing the entire inlet manifold and that involves a lot of unclipping looms, disconnecting electrical connectors and removing bolts.