94 Deville Radiator Fan Not Turning Fast Enough

I WAS WONDERING WHAT COULD CAUSE MY RADIATOR FAN TO RUN SLOW AND NOT COOL MY ENGINE LIKE IT IS SUPPOSE TOO. I HAD TO TAKE MY CAR TO THE E-CHECK STATION THE OTHER DAY AND IT DID NOT PASS BECAUSE THEY SAID THAT MY CAR WAS NOT COOLING DOWN ENOUGH. IT DOES'NT RUN HOT BECAUSE THE FAN IS TURNING BUT NOT FAST ENOUGH. I HAD AN 88 SEVILLE WITH THE SAME PROBLEM, I REPLACED THE FAN SWITCH AND ALSO THE FAN RELAY AND STILL HAD NO LUCK. I DIRECT WIRED THE FAN AND SOLD THE CAR ONCE IT PASSED E-CHECK. HAS ANYONE ELSE EVER HAD THIS PROBLEM? I REALLY COULD USE SOME HELP WITH TRYING TO FIX THIS PROBLEM.:banghead:

THANKS

Was the car overheating? I don't understand how they could fail a car because the fan wasn't spining fast! If you turn the A/C on, it should spin at full speed.