Thanks all for the input. I really dont have the exact history of the car maintenance as I have bought it only 5~6 months ago but as per my info, the previous owner was very meticulous about maintenance. Car has done around 150k km. And little that even I know is, 500 km ATF change is silly. Bhai 500km main tu aik tank bhi khatam nai hota tu....
And @leo_ali, ya 900 RPM is perfectly normal. Mine, when started and engine is cold, goes to like 1200 RPM for about 30 secs and then starts to calm down upto 800~900 RPM. And for engine so big -1800CC, AC does not make much of difference and RPMs remain pretty much same.
@capsat, thanks for suggestion and help and that is probably it but have you faced such/similar problem earlier? I am trying to find some
experienced opinion coz I dont wanna keep on going on hit and trial. Your opinion seems most logical and I will surely consider it. BTW, just brainstorming, what could be any other root cause for this problem?
Just on side note, other than this minor prob, this car is absolute pleasure to drive and I suspect, I wouldn't like any other local car anymore except a few..