My sons car idles at about 800rpm just a bit to low. It use to idle at about
900-950rpm. The engine has 60,000 miles. It's a 2 plug per cylinder 4 cylinder.If I unplug a switch next to the throttle body it will drop the rpms and jump back up when plugged in again, but not high enough.The engine has a rattle noise with the low rpms like it's going to stall. Give it just a little gas and it's quiet and idling smooth. Any idle on what I should be looking for? If I set the screw to get a higher idle then it runs on when I turn the car off.