Hi, My name is Joe. I am new to this Forum. This is my first post. I have a 2001 Dodge Dually 5 speed, manual transmission. Basically stock except for air filter and 4" exhaust. Engine is surging at 9 mph, as soon as you go over 9 mph, it idles up about 150 RPM's. It will do this in gear or in neutral coasting. As soon as you turn on the A/C it will stop surging and idle normal. I have taken it to the Dodge dealership twice and they can't find any codes. Any suggestions would be extremely helpful.