I'd like to share an issue that I'm facing with my corolla 03 (1.3 2nz-fe). The car has been running rich for the past few months. I've observed the following,
- Black smoke from the exhaust at mid to high rpms,
- Alot of smell of un-burnt fuel from the exhaust,
- Slightly erratic idle without the ac running. It idles at 1k rpm with the ac and is stable. Without it, while driving, when slowing down and bringing the car into neutral, the rpm sometimes drops below 400 giving you the feeling that the engine is about to stall and then comes back up to 700-750.
- Very poor fuel average. (Consumes fuel like a v8 except that it doesnt get you anywhere as fast as a v8 - its giving around 7-8km/ lit with a VERY light foot).
- Slightly sluggish at the lower rpm range.
- The car has around 270k km on the clock.
Now the things that I've already checked.
- Checked the injectors for leakage and cleaned them. They're fine and dont leak. The spray pattern is uniform too.
- Checked for vacuum leaks (the carburetor cleaner method).
- Recently replaced the fuel filter.
- Got the car hooked up to an OBDII scanner without any error codes. Too bad though that the scanner isnt working now for some reason or I would've posted a screen shot of the observations.
Now, I've looked up remedies online and the suggestions point to a faulty coolant temperature sensor. To test the sensor, I've taken voltage readings on it when the engine was warm (operating temperature) and it showed 0.5V. I have yet to check the reading with the engine cold and warm enough for the fan to come on automatically.
When the scanner was connected to it, I observed the coolant temperature to reach 97 degree C when the fan turned on. Is that the normal temperature for the fan to turn on?
I would be very grateful if anybody can help me solve this issue as its becoming annoying now and with the cost of fuel these days, very expensive to run too. @Xulfiqar your input on this would be much appreciated.
P.s. Sorry for the long write up. Had to let everybody in on all the clues And btw the car doesnt have cng installed.