Volvo: Volvo 740 GLE, volvo 740 gle, mass air flow sensor

Question
I have two questions about my 1990 Volvo 740 GLE (100,000 miles):
1) My check engine light came on and I took it to the dealership and they indicated that the error was the result of the Mass Air Flow sensor. Could you explain what this sensor does? The dealership suggested it be replaced. A few days later a aquantance removed the sensor and cleaned the small wires with a cleaner. This measure seemed to fix the problem. Is it detrimental to the car if this is not fixed ASAP as this part is rather expensive?
2) The other night I stated the car and it started but the headlights didn't come on and there was an awful screeching sound. I turned the car off immediately and restarted it. It sounded fine except for the check engine light returned. On a short drive on the highway for 30 miles the car seemed to lose power and seemed about to stall upon entering the city at a lower speed. I let the car sit for 6 hours and then re-started the car and it worked fine. Could this problem be related to the Mass Air flow sensor?
Thanks  

Answer
Hello Mark! The MAF sensor measures the amount of air coming into the engine. This signal is sent to the ECM where the fuel mixture is adjusted accordingly. It is poosible that you lost power due to the MAF sensor. It will also set the ck. engine light. The screeching and the headlight problem may be a separate issue.


Jimmy