So, in trying to diagnose my car's occasional cold start sputtering, it has sort of snowballed to where i'm about 95% sure I have a blown head gasket. My symptoms and discoveries are:

Frequent P0302 cylinder 2 misfire on cold start

Coolant is slowly disappearing, only from the post-thermostat side (upper rad. hose)

Coolant expansion tank is constantly full to the top with a small amount of oily residue floating around

The sound of bubbles in my dash (heater core)

The thing is, once the car misfires for 20 seconds or so, it runs totally fine and has never overheated. The misfire won't occur again until the car has sat for several hours.

Also, when I ran a compression test, every cylinder read 180, plus or minus 2 psi.

What I'd like to do is run a test to see is there are hydrocarbons in the exhaust but since coolant doesn't cycle through where our cap is on the expansion tank, I'm not even sure if one of those tests will work?

Does anyone else have a method for testing 100% diagnosis of a faulty head gasket? The car has about 90k miles on it, 2006 R53. Thanks!

 

Sounds like a leaking head gasket to me. And coolant does cycle through the expansion tank.

 

Some pretty good info on how to confirm it's the head gasket in this NAM thread here.