Gentlemen, I have a 93 500 SEL which has been a great car. It started cutting out after a trip of about `300 miles round trip. Bought gas at non brand station and was fine till next day. After starting the miss started.It has been intermittent and I thought was going to disappear after fresh fuel with water remover and injection cleaner. But is still acting up. How do I easily test injectors. Can I make a pig tail for injectors and power each one while connected to fuel rail with gas pressure to check for operation. If an injector is bad is there a source for reconditioned or reliable used injectors?
Also the heater stopped working. The duo-valve runs but no heat, there is some slight corrosion around clamps hose ends near firewall. How do I approach this diagnoses. Will the codes from AC/heat control module testing procedure help? Do I have to dismantle half the car to get the heater core out? Oh Forgot, there is no smell of antifreeze or radiator water in car. Recently replaced water pump but heater was non operative prior.
Paul in LA

Have you checked the fault codes on the 38 pin connector? With a stethoscope you can tell whether an injector is firing. Try a google search for injector cleaning and rebuilding. I know this one is good: http://www.cruzinperformance.com/ I'm not aware of any means of home testing.

I also had excellent results from Rich Jenson of cruzinperformance.com $16 per injector tested & cleaned. He also provides flow test results. My understandig is injectors should have same flow performance within a specific range.

Bob