Nissan Repair: nissan battery, air control valve, strange noise

Question
The AA came round to put a new battery in my car. The engine now works but
it's making a strange noise. The AA man said it's called 'hunting'. He said the car  
just needed a while to get used to the new battery but it's been a week and it's
still making this surging noise the whole time. How can I fix it?

Answer
Liz,

IF the idle is hunting you might disconnect the battery and hook it back up after about five minuted to let the computer zero out and se if that corrects the problem.  But, if you still have the idle hunting problem the idle air control valve is probably the issue.  A replacement is about $100 bucks plus labor.