ON MY 1987 RX I REPLACED THE THERMOSTAT AND MY ELECTRIC FAN WENT OUT BUT IT WONT GET WARM YOU WOULD THINK IT WOULD OVER HEAT BUT DRIVING DOWN THE HIGHWAY AT SPEED IT SITS RIGHT AT THE COLD MARK AND THE HEAT IS NOT VERY WARM NOW IF I SIT AT A LIGHT IT STARTS TO GET WARM BUT THEN COOLS OFF AGAIN WHAT CAN I DO TO FIX THIS 

Add more coolant!!You likely have air trapped in the cooling system

 

Park your car nose high, so your heater core is no longer the highest point in the system. Blast the heat, run your car with the radiator cap off.

keep an eye on your coolant level. 

let it get up to temperature and let your thermostat open, make sure your upper hose gets hot too. add more coolant as air bubbles out.

 

Continue until no more air is coming out of the system. It may help to work the air out by massaging the upper hose.

 

You can speed up the warm up process by running the car at about 2,000rpm

 

That should do it, good luck, awesome car by the way. It looks best stock height.

thanks i will try that i like it back to stock height