Mitsubishi Repair: 92 Eclipse Starting problem, coolant temperature sensor, mitsubishi eclipse

Question
Mitsubishi Eclipse Turbo 1992, 128K miles
The car has intermittent starting, idle is low during warmup and after warm up I see lot of smoke coming out of the exhaust at the rear end. I kind of smell half burnt gaoline at the exhaust. The car also stalls intially. When the engine is really hot and has been driven for a while(say 15 minutes ) the car runs smooth but the check engine light comes on intermittently during driving. Also when the car is hot and I put in in idle the smoke is more from the exhaust.
The car runs smooth if I start and leave it for 15 minutes to idle.

What could be wrong and what Should I do?

Thanks in advance.

Answer
Anand,
It sounds like you could be having a problem with your O2 (oxygen) sensor and/or your coolant temperature sensor.  The indication for a malfunctioning O2 sensor is poor idle after the engine has warmed up, lower gas mileage, and dark colored smoke that smells of fuel that exits your muffler.  A malfucntioning temperature sensor can also cause poor idling when the engine is warmed up.

If you have an AutoZone in your area, they can scan your car's computer for free.  That may determine why your check engine light sometimes comes on.  And if the check engine light comes on and stays on, definitely have the car's computer scanned for trouble codes.  And if you do not have an AutoZone, you can take your car to a mechanic and ask them to test your O2 sensor and coolant temperature sensor.  It won't be free, but they will be able to determine if the sensor are working correctly.
Good luck!