Honda Civic

I’m from Pakistan and own a 1994 Honda Civic EX 1.5 with 5 speed M/T and carburetor (chassis code: PK4). The car has done 174,000 km and has been regularly serviced. Recently I have noticed that the car starts emitting black smoke and soot from the tail pipe after a while of idling. If left unchecked, the engine becomes rough, the rpm starts falling and the motor finally dies. However, if I rev up, the engine picks up after emitting a moderate amount of black smoke from the tail pipe and runs fine at all higher speeds (no smoke, no loss of power). Let me also mention that I have a slight leak in the cooling system (probably in the gasket) and will soon be taking the car in for necessary repairs. In the meantime I regularly check the coolant level and top up if required. What is my problem at idling? Could it be related to the cooling system leak? Any help will be appreciated.
Dr. Tariq Hakim
January 19, 2006.

I am just a regular person who likes cars, but here are my two cents: black smoke usually means engine oil is leaking into the engine. Colored smoke means other types of liquids are leaking into the engine. The color of the smoke or burnt liquied will tell you what is burning. Any colored gas (black, red, blue, etc) coming from exhaust is NOT good.

Only white vapor is normal during humid or cold days due to condensation.

Jan 22, 2006.
Agreeing with other post and/or as well sounds like an o2 sensor giveing a foul reading at idle. And with that mileage maybe a clogged catilatic converter. Good luck

Jan 22, 2006.
Maybe it is running too rich, when the problem occurs?

Nov 21, 2010.