Thanks for reply Fahad:
Fan was AUTO; Thermostate was installed whole winter. (i changed both yesterday for AC performance;) When they are intalled and AUTO, same issue was present, and after changing! again same. I think these don't effect my problem.
And yes! if i start it on Petrol (only petrol) and then switch it manually after 3 minutes, it works fine.
But all i want to discuss is the EFI's attractive feature that if last night i parked the car on cNG, next morning, engin will start on petrol, and auto switch to CNG. here comes the problem, this auto switching time is very low; so that engine don't get enough heated to switch.
Can we alter this time of autoswitch from petrol to cng ?
In the EFI's behavior discussed above, initial start is done over petrol and then auto changed to CNG, I like it very much so my mind don't accept manual switching from petrol to cng. It is surely a bug, and i want to solve it with YOU PEOPLE's help rather than just compromise and do the CNG/PETROL switching manually.