I have a 2008 Chevrolet Silverado, 5.3 L, Z-71 4x4, crew cab. I have been experiencing a very frustrating issue for the last few months. While idling (in park or sitting at red light etc..) the engine Rpms will suddenly drop to around 200 then rev back up to around 800 rpms then settle out to normal idle speed. Occasionally when this happens the engine will not rev back up and will completely die, however it will always crank back up. This issue happens intermittently, sometimes multiple times while driving, sometimes will not happen for several days. Also this will happen intermittently while at any speed however the engine will not completely die but lose power for less than a second causing check engine light to blink on then back off. Took to dealership....there are no codes. They cleaned the throttle body and Changed the positive battery cable. Neither had an effect on the problem. ANY insight would be much appreciated!!!