I got an 02 dakota with the 4.7. It has a crazy idle while in park and neutral. Also the rpms bounce up and down (about 300rpm) while I'm driving, but only after about 45 mph. It's not throwing any codes and I have no idea where to start. Any ideas?

 

Start off with cleaning the throttle body. Take it off the vehicle to do this. Make sure the IAC passages are nice and clean.