I had the car set to 750 idle RPM in Park. When I go into Drive the rpm drops to the 400s. The car runs fine and is smooth however when I put on the A/C the car instantly misfires and with intermittent stalling on the road when approaching stop lights or at a stop light. If I stop at a stop light it will shut off more times than not. My guess is the RPM drops even lower to high 300's when AC is engaged though its hard to tell on my dash RPM reader. If I turn off the AC and try and get the car going after it starts intermittent/misfires forget it, it keeps misfiring. The engine is totally compromised by that point and I have to wait a good 15+ minutes to get back home with some hiccups along the way.

My solution that I don't think is great but is working:

I adjusted the idle screw so I'm running around 900-1k idle rpm, then in drive it drops to 700-750 and I can run AC and car is fine. AC is cold and engine never misfires and I can drive it anywhere with no issues and good power in the engine.

What would the problem be and is it ok to run the car this way? Should I get it checked out or just drive this way.

Thank you!
Ethan

1979 244 DL
Automatic 5-speed transmission

 

Well, you are on the right track. Your solution is the correct one; if the idle is too low the engine will sputter when it gets slowed down be it by the A/C or the tranny. What is the factory recommended idle speed? It doesn't really matter at this point. Having it at higher idle so it runs well is fine--900-1,000 RPM is acceptable in my book.