when you stop in traffic with the ac on the engine cuts off. if you turn it on with car idling it runs funny when u turn it off like it isn't turning enough rpms or something but runs normal when u give it some gas. we took it to the nissan place they said some sort of valve was the problem and it would cost 300 to fix it. damn i have to many problems with my car. this ones, door locks not working, the gas tank opener lever won't open the gas tank, and its leaking oil near the alternator.