Had a scanner and it told me to replace idle air control valve, after replacing it, I still get the check engine light. Car is not surging and happens only when parked, not driving. RPM is 1000-1200

First... telling us a little about the car may help. The code may help also.

2nd, scanning doesn't always give you a dead-on diagnosis of a problem. Many things can set off a code that aren't actually the part itself.

First time it throws P0505, 2nd hey scanned and light went off during scanning... no codes

I can't really diagnose this online but you can read this:

http://www.obd-codes.com/p0505

Also, check for vacuum leaks.

First, clear any old codes with the scan tool.

On many cars, you warm them up to normal operating temperature, disconnect the IACV electrical connector, set the idle to the Initial Idle Speed, reconnect the IACV connector, and reset the ECM.

Thanks for your help.. read that link and the engine does not stall while parked, no surging and happens only when I take off accelerator during driving,disconect the battery and is OK until next check engine light on