P1100 FORD -

Question

Just recently brought my 99 Ford explorer to mechanic because of Check Engine light. They determined the Mass airflow sensor code came up and replaced the old one with new. Got my vehicle back and brought it home with no Check Engine light. About 4 hours later got into my car and the light turned back on. And now when my car is idle and I slowly accelerate, the transition to movement is not smooth but choppy. What could be the cause of this new added headache?