My X20 begin to act very weird for this couple of month. It's best describe as mentioned below. I thought it was the VVT sensor was dirty, had it clean and the engine run smoothly but the problem repeating again. I even change the VVT sensor..the problem still exist.
After doing some reading, I finally decided to check on the MAF sensor.
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Using a size 10 ring spanner, I manage to removed the MAF sensor. It was oily and dirty.
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Using a small brush and Electro Cleaner, just spray the cleaner generously and lightly brush the sensor. After installing, the engine is back to life as before.
It's a simple task. Should the problem arised, perhaps I should change the MAF sensor as the car already 9 years old...wear and tear beginning to show.