93 fd weird cold start at 500rpm
 

Hello fellow fd owners, I came from sti evo m3 world, this is very new to me, I've done so many searches on our motors but I can't seem to find the answer to my issue.....
Ok my 93 fd starts cold at 500 rpm then goes up to 1500-1600 rpm and stays there when warm, kind of odd, I noticed the o2 sensor was cut, I didn't notice any leaks from normal upright visual, I sprayed around the engine bay to try to identify any air leakage, and non, I am guessing its a vacuum leak but not sure, any one knows wats going? Or have encountered such problem? Thanks

Correction it's starts cold at 1000-1100 rpm, alternator was rebuilt from previous owner, it puts out 15 volts when car is off, when car is on the head lights, tails and interior lights are throbbing

From what I read these cars are designed to rev high a little at start up to warm up faster. If you hit the gas pedal or put it in gear the Rpms should drop. Even at 1000-1100 Rpms that's not crazy. Mine goes up to almost 3k for a minute or so. These cars are only supposed to idle around 750 anyway. What mods are done

No mods done, I noticed the o2 sensor was cut and the previous owner adjusted the idler to 1300 so the car doesn't keep shutting off on him