Thanks Horse_rider for your suggestion. So one thing is cleared that there is no "Check Engine Light" in 2003 Santro.
After about 50km drive, I have clarified the issue regaring rpm increase. Whenever I press the cluth and a slight race, the rpm increases and doesn't come back until I press the break paddle. It is very irritating when driving inside city as muree road where car is stuck in traffic and have to move inch by inch :(. Could you please identify which part is causing the issue? has anyone faced this before?
One question more, what will be the checkup cost at "Sawan Motors" if I visit there? I have heard that they are much expensive.
Also I calculated that my car is eating CNG drove only 55KM for 275Rs CNG:$ where to go for CNG Tunning?