Idle speed adjustment

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07-29-2006, 12:47 PM

88'F150

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Idle speed adjustment

As a new member here, I have already found some very valuable information. Thanks Old_Paint for the information on the intake manifold. I was having the same problems.

I have read many posts wanting to know how to set curb idle or reset the adjustment screw. The following information comes from a site I have a subscription to.

Idle speed

NOTE: A change in idle speed occurred because of a problem elsewhere. Enter this procedure after eliminating the possible causes listed below:

Contamination within the throttle bore and/or idle speed control device.
Throttle sticking or binding.
Engine not reaching operating temperature.
Vacuum leaks (air intake, vacuum hoses, vacuum reservoirs, power brake booster, etc.)<O

VERIFY:

Transmission is in PARK A/T or NEUTRAL M/T. <O
Parking brake is APPLIED (automatic brake release is DISCONNECTED where applicable).
<OWheels blocked.
<OCooling system is filled to proper level.
Engine is at operating temperature.
All accessories (heater, radio, lights, etc.) OFF.
Throttle lever is resting ON the throttle plate stop screw.
Ignition timing is set to specification.
Perform EEC-IV diagnostics and resolve any vehicle malfunctions that are indicated by service codes. (Ignore this step if sent here from an EEC-IV Pinpoint Test step).

Engine OFF, disconnect the negative (-) terminal of the battery for 5 minutes minimum, then reconnect it. NOTE: Memory to radio, phone, and other programmable accessories may be erased when the battery is disconnected.

PROCEDURES

With engine OFF install specified feeler gauge between throttle plate stop screw and throttle lever. Automatic transmission .050 inches, manual transmission .030 inches.
Unplug SPOUT line and verify that ignition timing is 10°+/- 2°BTDC. <O
Disconnect idle speed control-air bypass solenoid.
With transmission in NEUTRAL (M/T) or PARK (A/T): Allow engine to idle for 2 minutes.
Check/adjust idle rpm: Turn the throttle plate stop screw to 675 +25 rpm automatic transmission, 700 +25 rpm manual transmission. NOTE: If you must turn the throttle stop screw IN, turn engine OFF, make estimated adjustment. START engine and repeat Steps 4, 5, and 6 before continuing.
Shut engine OFF and disconnect battery for a minimum of 5 minutes. NOTE: Memory to radio, phone, and other programmable accessories may be erased when the battery is disconnected.
Remove feeler gauge from throttle plate stop screw and throttle lever pad.
Reconnect SPOUT line.
Turn engine OFF and reconnect idle speed control-air bypass solenoid, verify the throttle is not stuck in the bore and linkage not preventing throttle from closing.
START engine and stabilize for 2 minutes then goose engine and let it return to idle, lightly depress and release the accelerator. Let engine idle, if problem exists, see Diagnosis by Symptom (Diagnostic Routines.) NOTE: A condition may occur where the engine rpm will oscillate. This can be caused by the throttle plates being open enough to allow purge flow. To verify this condition, disconnect the carbon canister purge line and plug it. If purge is present, the throttle plates must be closed until the purge flow induced idle oscillations stop.
On Automatic Overdrive Transmission (AOD) applications check TV pressure adjustment.