I did some searching about our problem and found some quite relevant discussions:
Post 12 and 13 (I guess this does not directly apply for our cars since they have hydraulic tappets):
http://www.subaruforester.org/vbulle...ing-lpg-35882/
Various causes but more or less "trivial":
http://www.aussiemagna.com/forums/ar...p/t-77298.html
http://forums.mercedesclub.org.uk/ar...p/t-10875.html
http://forums.whirlpool.net.au/archive/1849550
You might go through these discussions and maybe you will get a hint... I got a few:
- there might be some valve clearance problems when the engine is cold and the gas leaks... I don't know how to check this.
- some not-metered air comes to the intake manifold... But from where? False vacuum solenoid valve?
- could it be some vacuum leak... But why only when engine is cold?
- the air filter is dirty... Again, why only when engine is cold?
- maybe someone could help on this forum:
http://www.lpgforum.co.uk/
The temperatures are getting lower and lower...
Jan