2001 Kia Rio

I’ve got a KIA RIO LS TOP purchased in December 2001.

After about two years, very often the yellow check light turned on.
Soon I took the car to KIA Service Centre of my City.
They checked the events memory and diagnosed the problem was caused from the debimeter/ air flow meter malfunction.
They replaced it and the problem was solved.
But not much time after, very serious problems began.

Read below.

a) the minimum RPM is not uniform. The situation gets worse if I use air conditioned;
b) the car runs with speed not uniform. The RPM increases and decreases without to use the accelerator;
c) very often I take away the foot from the accelerator and the RPM doesn’t decrease, even if the accelerator pedal is off. Only after some seconds (5-7) the RPM decreases.

When the mechanic checks the car the computer’s display shows : NO DEFECT.