Just lately when i start my 93 jdm supra tt the rpms will start from about 500 and try to go up then fall back down and shake a little, and then idle fine at around 800-900. Is this just because of a cold start?
Did you disconnect the battery or reset the ECU recently? Usually you will see this startup idle problem on an ECU reset. It improves with time as the ECU relearns the short term fuel trims.