oil in spark plug and 5 cylinders

[90Degrees]

hi there, a friend of mine is having some issues with his m20. Theres seems to be oil that gets trough to one of his spark plugs and he's running on 5 cylinders now. Bubbly, like harley sound. Before it would start up on 5 then after a few seconds everything would be ok. But now it stays on 5. Do you guys have any ideas on what could be the cause ?

[whodwho]

Start with a compression/leakdown test and see how the basic engine is, if it is low/bad then there is some major work needed.

[90Degrees]

nvm, i went to check and two spark plugs were not screwed correctly.

[sonnyqm3]

check the valve cover gasket. might be a good idea to change the gasket..

[90Degrees]

yup, im adjusting his valves this afternoon and were changing it too.