Mustang V8-302 5.0L COBRA (1995)
Idle Speed: Adjustments
NOTE: The curb and fast idle speeds are controlled by the Powertrain Control Module (PCM) and Idle Air Control (IAC) valve assembly. The IAC
valve is not adjustable. A large increase or decrease in closed plate airflow from the calibrated level will not allow effective idle speed control.
The throttle body incorporates an orifice in the throttle plate controlling idle airflow as part of the sludge tolerant design.
Throttle Body Assembly Decal Location
Throttle bodies with sludge tolerant design are identified with a yellow/black decal. This decal warns that the throttle plate stop screw must not be
adjusted counterclockwise (backed off), as this will not reduce the engine speed but may cause the throttle plate to stick in the bore. Backing out the
screw may be required if the throttle body has been previously serviced (a plug in the throttle plate orifice may be present), or the plate stop screw
tampered with (TP Self-Test output out of range). The decal also warns that the throttle body must NOT be cleaned inside the bore, as this cleaning will
impair the sensitive coating. The sludge accumulation will not affect the idle air flow. The cleaning procedure for the IAC valve still applies.
REMEMBER
A change in idle airflow can occur not only at the throttle body but other areas as well. You should enter the idle speed procedure only after other
possible causes in the following areas are eliminated.
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Contamination within the idle speed control device
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Lack of fuel system control (excessively rich or lean)
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Throttle sticking or binding
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Engine not reaching operating temperature
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Incorrect ignition timing
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Incorrect or clogged PCV system
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Vacuum leaks (intake manifold, vacuum hoses, vacuum reservoirs, power brake booster etc.
VERIFY
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Transmission is in Park (A/T), or Neutral (M/T)
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Parking brake is applied (automatic brake release disconnected where applicable)
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Wheels blocked
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Engine at operating temperature
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Proper fuel pressure and no exhaust smoke
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Correct and clean PCV system
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Heater, A/C, and other accessories Off
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Ignition timing is set to specification
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EEC-IV diagnostics have been performed and vehicle malfunction indicated diagnostic trouble codes have been resolved.
PROCEDURE
STEP 1
With the engine Off, connect a tachometer according to manufacturers instructions. Disconnect the negative (-) terminal of the battery for 5
minutes, then reconnect it.
STEP 2
Start the engine and allow the idle to stabilize for two minutes. Goose the accelerator, and let the engine return to idle. Lightly depress and release
the accelerator, then let the engine idle.
