Causes of Idle surging

[rateeb]

I have a question for those who really have good knowledge about idle surging in a car. Can anyone discuss the causes of idle surging in a car and how can we prevent our cars from surging. 

[lonely]

Well I know that when the air comes inside the cooling system, it causes idle surging. I faced the similar issue before, and I was reported idle surging.

[ronaldeve]

Another reason that causes idle surging is bad head gasket as well. That is something serious because it needs complete replacement.

[bhushandxb]

Another reason that causes idle surging is bad head gasket as well. That is something serious because it needs complete replacement.

[rateeb]

Can you tell me how much is the replacement for head gasket.