Brought Dart to shop to fix idling issue and car runs like s**t!

A lot of good stuff here, especially for someone like me whose trouble-shooting skills are rusty and out of date. I’m still chanting “ignition, carburetion, compression.” One of my favorite trouble-shooting tools is a cylinder-shorting dwell tach (Snap-On MT460) that I used to sell back in my days as a Snap-On dealer. It was the control unit for their oscilloscope, but you could buy it separately. I sold more scopes (and AVR testers) than any dealer in the Phoenix branch back then because I would train my customers on how to use them. I still miss oscilloscopes too, although modern computerized engine controls have largely made them irrelevant. A quick search revealed several MT460’s for sale on ebay for very reasonable prices. If you have an older car with battery-point ignition, they’re worth a look. I’m pretty sure you could pick the adaptor harnesses for early electronic ignitions like HEI, etc., too.