Ford Repair: 1999 Explorer almost stalls when stopping after highway run., mass air sensor, mass airflow sensor

Question
I have a 1999 Explorer that nearly always nearly-stalls when stopping after exiting the highway.  Doesn't do this while running around town.  When coming to a stop after running a minimum of 10 minutes on the highway at 100+ km/hr, the engine drops to around 100-200 rpm, chugs a bit, then comes back up to speed.  Fuel mileage has been a bit worse since this started (about 5 months ago.  Check engine light does not come on.  No error codes are generated.  No very obvious vacuum leaks (I have looked and listened).

Thanks,
AndyC.


Answer
Andy:

There are multiple possibilities for your concern including but not limited to Idle sped control, mass airflow sensor, intake manifold gaskets (more prevalent on 4.0 sohc), or bad mass air sensor (poor fuel mileage and erratic idle).  If the erratic idle starts to happen when cold I would suspect idle speed control motor.  

Hope this helps

Patrick