Exhaust black smoke

Dears,

I diagnosed a Toyota corolla 2010 1.8L engine with black smoke issue. The only DTC was P0420 catalytic converter issue. I monitored the downstream sensor, it had too much activity on it. So, we replace the catalytic converter. The smoke is less but it is still there.

Fuel trim is within a reasonable range that doesnt pass over 10 (STFT and LTFT).
Black smoke is indication of rich condition. I tested all maf, injectors, air filter, spark plug, COP and even replaced the fuel return pressure regulator. The smoke is still there.


Any suggestion and diag method are highly welcomed.

Thank you.

Is it using oil ? Toyota had cylinder bore wear issues on some 1.8 engines around that model year, over here in the UK they replaced a lot of engines out of warranty as a goodwill gesture.

Moved topic to Repair section.

naros812000 wrote: Fuel trim is within a reasonable range that doesnt pass over 10 (STFT and LTFT).

Running rich, with positive full trims.....

I monitored the downstream sensor, it had too much activity on it

How is the activity on the upstream sensor? I would expect to see a pegged rich O2, if it was rich enough to be smoking.

I don't think I believe your Upstream O2 sensor. Can you create a vacuum leak and lean the upstream sensor out, at all? Add propane to the intake? Any reaction?

I'm with pole71, I dunno that the upstream sensor is telling the truth. If you find that it reacts, and that the downstream sensor generally agrees, then I'd question if the smoke really is a result of a rich condition. Possible oil consumption, like Andy mentioned?