I'm pretty sure you have basicaly answered your own gestion by stating the problem is resolved when you clear the ecu. I'm sure if you ran the car on petrol only the problem would not arrise.
It looks very much like your LPG mapping is out - not much of a suprise for a single point system on a 960. The qucik easy answer would to be to by and fit a ecu reset modul to clear teh ecu every time you switch off.
|