A faulty mass air flow (MAF) sensor can cause erratic/rough engine operation and fuel economy issues. Since this sensor measures the actual amount of air entering the motor, when it fails, the engine control module (ECM) takes the wrong information and delivers incorrect volumes of fuel to the cylinders.Google+
Car Problem Reports
Mercedes-Benz SL320 Faulty Mass Air Flow Sensor Causing Erratic Engine Operation and Poor Fuel Economy
Mercedes-Benz SL320 Problem
Visitor, 1994 Mercedes-Benz SL320, 56,000 mi
Engine surges during warm up and sometimes when fully warmed. By surges I mean when driving slowly (20 - 25 mph) at fist start up the car will sometimes surge several hundred rpm the go back to normal rpm the surge agan several times over the course of one or two minutes. Sometimes when fully warmed it will surge the same way when I am in reverse and idling in reverse while backing up, can also happen when idling in forward while parking the car.
Not fixed, looking for what I should be looking into