Smoke from tailpipe (CRV 1st Gen)

[GBStJames]

Guys!
I have this weird situation with my crv. Right after start up, and while idling di naman mausok yung tambutso. Even if I start it early in the morning. Yung normal steam lang nakikita ko. Pero after driving for around 10 km, mausok na yung tambutso. Napansin ko din na nangyayari ito sabay ng pag-on ng auxillary fan. In short, di naman consistent yung pagiging mausok niya. May mga times ok lang. Kaya di rin masabi nung mechanic ko kung ano cause kasi tuwing dadalhin ko sa shop, di na uli mausok.
Any ideas?

[GBStJames]

Follow up ko lang po ito. I brought the car to my mechanic this morning habang mausok pa yung tambutso. Sabi nya ok naman yungengine kaya ang hirap i-diagnose kung ano yung cause ng usok. Yung kasama nya sa shop suggested to remove the muffler. That seemed to solve the problem. Halos nawala yung usok. So we decided to change the muffler. Pinaalis ko na rin yung catalytic converter. Pero may usok pa rin. Kaunti nga lang kumpara sa dati. I see other 1st gen CRV na talagang walang usok na lumalabas sa tailpipe nila.

[atog]

sir cheak if white smoke..cheak oil condition,spark plugs,air filter,valve tappet clearance,at ignition timing sir..