97 Ford Explorer Idle Air Control Valve Symptoms
The 1997 Ford Explorer has a fuel-injected engine with the fuel injectors located in the intake manifold. The throttle body takes the place ...
The 1997 Ford Explorer has a fuel-injected engine with the fuel injectors located in the intake manifold. The throttle body takes the place of a carburetor used in early model vehicles. The purpose of the throttle body is to meter the correct amount of air entering the intake manifold. A large round throttle plate at the opening of the throttle body opens and closes with the accelerator pedal. At an idle, the throttle plate is closed preventing any airflow into the manifold. This is where the idle air control IAC comes into play.
Location
The idle air control is mounted on the side of the throttle body and is aligned with the throttle plate. Two holes in the side of the throttle body one in front of the throttle plate and one behind are directly under the idle air control. Its with these two holes that the IAC meters air in sufficient quantities, through ECU control, to maintain a perfect idle.
Operating Principals
The IAC has two holes in the bottom mounting surface which, when installed, correspond with the holes in the throttle body. It is essentially a reversible electric motor and operates a screw mechanism capped by a cone shaped piece called a pintle. The pintle enters and exits a port that interconnects the two holes in its base when commanded by the ECU to do so.
The position of the pintle in the IAC on the 1997 Explorer makes numerous adjustments every minute to control the idle. The load on the engine at an idle varies with the cycling of the air conditioning, loads posed on the alternator and so on, all of which directly effects engine rpm.
Symptoms of a Failing Idle Air Control
As its name implies, the idle air control only operates at an idle. This is primarily where the symptoms will present themselves. The most classic symptom is a surging idle the idle will rise and fall repeatedly. This symptom can be caused by a fouled idle air control spring and shaft, which slows the movement of the idle air control and makes it difficult to keep up with ECU commands
An engine that is difficult to start and will not idle without accelerator assist indicates that the IAC is stuck in a closed position. Any type of rpm issues, such as an excessively high idle, the engine will not return quickly to or returns very slowly to idle when the accelerator is depressed, the engine stalls when coming to a stop due to excessively low idle, it stalls at an idle when the air conditioner is turned on or if the idle rpm continues to climb at an idle are all symptoms of a faulty IAC.
Causes of IAC Failure
The primary cause for IAC failure is carbon and oil fouling of the pintle and motor. The pintle shaft threads into the motor. When the threads become carbon or oil fouled they get hung up and the pintle will either move very slowly or not at all. When the pintle fouls, it will stick in whichever position it is in at the time.
Rectifying the Problem
Cleaning the IAC is effective 5 percent of the time and doesnt last long. The best way to solve this problem is to replace the IAC completely. It is very simple to replace. Unplug the electrical connector and remove the two bolts securing it to the throttle body. Install a new gasket and the IAC in the reverse order of removal.
