do i have gearbox problem - used kia sportage 2005 (B) on 2005 Kia Sportage

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when the car moves it does not does not change gear smoothly and off and on there is a "check engine" indicator on. Now it can only reverse easily but i find it difficult to engage the D gear. Do i have gear box problem or where can i get my gear box replace in Bandar Baru Bangi, Selangor, Malaysia? How much will it cost me?
(1) Answer
you may need to change the air filer. i have this car and i have to change the air filter every month or it won't shift correctly . it sounds crazy, but its a problem, it will start hanging up in gears if the air filter is not perfectly clean