Clogged Fuel filter, Leaking of injector, timing too much advanced (Due to cng installed ). Check for these first. I had a same issue couple of months earlier, culprit was abnormal spray pattern of injectors so i replaced them.
P.s. The mileage is very poor i get around 12 in AC (Light foot & shifting below 2500) & without AC 13.5 to 14 on petrol. Engine is D15