My idle has been kind of weird as of late. My normal idle is roughly around 750 rpm, but I have been noticing that after driving for at least 15 min, when I stop, sometimes my idle drops down to 600 rpms, then goes back up to around 700-750. Any ideas?

 

maybe just some bad gas. fill up with some 76 super unleaded and add a little pettit premix. did this to mine and idle is smooth , and vacume psi went up a little. the premix made the motor smooth and quiet.
Jeff

 

The few times I've suffered from an erratic or hunting idle it has been because of a leak in the intake system or Air Pump system.