After a bit of advice, I've had this issue for a few years and the fuel consumption is making me want to fix it. This all started about 4 years ago and have just put up with it but the fuel is getting worse, currently getting about 350km around town driving moderately (I used to get 450km driving the same way...).
When the engine starts cold it will sound like there is a miss for the first 3-4 minutes. The exhaust has white smoke, very faint though with a very small hint of blue (sometimes). Though the engine oil barely drops between servicing (I change the oil every 10-15k). After 3-4 minutes of warming up the car drives fine, no loss of power.
I recently drove a 3,000km hwy trip and noticed the back of the car was full of oil, obviously from overtaking and putting the foot down.
Things I've checked:
new spark plugs
Checked all coils (using servicable one, replacing one by one)
Re-flashing the ecu (I have 3 maps and tried them all)
Replaced the PCV
Checked all hoses visually
Compression check
I'm suspecting a valve seal is gone or valve spring. My next move is to take the head off and get it recon.. though hoping someone here has a more likely cause, I.e if its the springs or seals would it be worth changing them first rather than take head off?
The car is an xr6t mkII with 200,000km, 330rwkw and was tuned 7 years ago running 14psi. I've driven in pretty hard and only since this problem have eased off a bit on the lead foot.
