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ISC Motor ( Idle Speed Motor)

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yo, You habe an 89 Bronco II, right?


Idle Air Control (IAC) Sludge; Poor Idle TSB 91-25-07 for 85-92 Bronco & F Series & many others; "...Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions. Hard Cold Start, Stall On Initial Start-Up, Stall During Idle, Stall During Decel, Rough Idle, Rolling Idle, Hesitation During Acceleration. A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only. It eliminates the need to clean the majority of past model throttle body applications. Cleaning is not required on sludge tolerant throttle body designs released for 1991 and newer model years..." Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net


Click on the baove and read through it; it is long, detailed and exact as per Ford's instructions...

some think it's too long to read & miss the important info.


The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows air, determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed.

Removal & Installation

1.To remove the IAC valve, first disconnect the negative battery cable, then the IAC wire harness plug


Next, remove the two IAC valve attaching bolts ...


... and pull the valve from the intake manifold

2.Disengage the wiring harness connector from the IAC valve.


3.Remove the two retaining screws, then remove the IAC valve and discard the old gasket.

When installing the valve, always discard the old gasket and install it using a new one

by Ford & CHILTON

4.Clean the IAC valve mounting surface on the throttle body of old gasket material.


5.Using a new gasket, position the IAC valve on the throttle body. Install and tighten the retaining screws to 71-106 inch lbs. (8-12 Nm).


6.Attach the wiring harness connector to the IAC valve.


7.Connect the negative battery cable





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I couldn't load the last pic for some reason;

Idle or Stalling Problems & Troubleshooting; "...The IAC is usually a cylindrical unit attached to the upper intake manifold. This unit electrically controlled by the computer, and allows air to flow into the intake at idle, bypassing the throttle plate. The extra air is accompanied by extra fuel to bring the idle up to proper speed, and when cold, allows a high idle condition. These units may become dirty, and need cleaning. Many idle and stalling issues tend to be blamed on these units. Cleaning is achieved by removing the electrical connector, and two screws holding it on. Once off of the vehicle, clean with throttle body cleaner (or a good carburetor cleaner). Continue cleaning until unit is clean, like new; reinstall unit. This is also a good time to clean the intake, and EGR ports (if applicable). Testing may be achieved by bringing the engine to operating temperature, noting the idle speed (should be within spec). Unplug the unit’s electrical connector, and the idle should drop to about 650 RPM. When the unit is reinstalled, it should return to normal idle speed. If the vehicle does not idle at proper RPM (too low), there are no vacuum leaks, and the TPS calibration is correct, than the unit is most likely fault..." Source: by broncoii.org

& more testing;





1.Turn the ignition switch to the OFF position.


2.Disengage the wiring harness connector from the IAC valve .


3.Using an ohmmeter, measure the resistance between the terminals of the valve.


Due to the diode in the solenoid, place th89684g36.gife ohmmeter positive lead on the VPWR terminal and the negative lead on the ISC terminal.


4.If the resistance is not 7-13 ohms, replace the IAC valve.


Overview & Testing; "First let me say this little thing has many names. But they all talk about the same item under the hood. Here all the names I’ve had the torture of learning throughout the years: Idle Air Bypass •Idle Air Control •Idle Speed Control •Throttle Bypass Air •Idle Bypass •Inlet Air Controller •Inlet Air Bypass •Intake Air Bypass •Intake Air Control..."

Source: by Ryan M (Fireguy50) at http://fordfuelinjection.com/index.php?p=39

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