The idle speed is electronically controlled y an idle air control motor (IAC). A computer in your vehicle takes in inputs from various engine sensors (it looks at engine temperature, present idle speed, engine load, throttle position, and whether the air conditioning, power steering of electrical loads are on or being operated), the computer processes these inputs and decides what the idle speed should be. It sends a signal to the IAC to determine what the idle speed should now be. The idle speed can only be controlled so much. If the engine has other problems like vacuum leaks, ignition or fuel system problems, or engine mechanical problems these problems may put controlling the idle speed beyond the parameters by which the computer can control the idle speed.
Check that the engine is running OK, ensure there are no trouble codes or pending codes stored in the power train computer in your vehicle and check that the idle air control motor is functioning.
For the same vehicle, my motor is also shutting off, apparently due to low idle.
But it is otherwise running good and there are no error codes. Can anyone advise what else to check?
2006 E-250, 4.6L
This problem just started yesterday. The motor just shuts off letting off the gas after cruising. The motor will run OK at a standstill. There is no high idleing.
I have only driven this vehicle about 200 (just two hundred) miles since I bought it about six months ago. It has 191,000 miles on it. I just changed the battery and starter. It has always idled at a very low speed. But the motor never shut down before.
I am going to check the air filter now.