AE86 Engine Coolant Temp Sensor

[Bean]

Have you set the TPS? The sensor has to be adjusted right else the ECU won't go completely into idle mode. You'll find the procedure in the manual.

Also make sure you don't have any leaks in the plenum and that your throttle body flap is closing all the way. After some decades it can use a good clean.

With the idle adjustment screw fully in your engine isn't supposed to run as there's not enough air to get even to 500rpm