what is the wrong with my car?

i have a problem with my car the thing that the meter of the rounds of the engine is not stable....the car continue to uneven rhythm and eventually it shut down ...... many people had told me that it is air flow problem...... i changed the electronic device that is responsible for the regulation of the air flow if worked well for few days and relapsed again but i am not sure the new device i bought is good cuz it was used and i gave it back to the shop since it was in the warranty period....i just want you to confirm that the problem is with the air flow....by the way the thing that this is not continous when i clean this device and put it again it works good...and i also changed the fuel pump to be sure that it was not the cause i will be gratefull to answer me ..thanks

hyder
September 2009