My 82 5 speed with new rebuilt engine had developed a surging idle when warm. Idle speed would go from 800 to 1300 rpms while at a stop light and only shutting off engine and restarting would sometimes fix the surge.

I replaced the original 31 year old O2 sensor with a Universal unit I got from Roger and the surge went away. After I adjusted the idle, she runs great.

Hopefully my MPGs will improve a little as I think she was running a bit rich.

 

Good advice!