miata check engine light

I have a 92 miata with 84K miles. Although the mass air flow sensor has been replaced I still get a check engine light approx 2-3 minutes after a cold start. Get intermittent lights and it usually goes away when the engine warms up after approx 10 minutes. Sometimes after it goes out and the engine is not completely warmed up (eng temp gauge at 10-11 o'clock position, the idle gets stuck at 1800 rpm. Usually idles normally if the engine completely warms up (gauge at 12 0'Clock).