FUEL-08, Idle Speed Adjustment


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Introduction

Idle speed adjustment is not normally required on 944s. However, the idle speed adjusting screw will sometimes back out causing idle speed to become out of adjustment. The 944S and S2 models use a system called "adaptive idle speed volumetric efficiency regulation" and do not require idle speed adjustment.

Tools

Idle Adjustment

  1. Turn off the fan motor and AC Compressor during idle adjustment.
  2. Start the vehicle and allow it to idle to warm up the engine. The factory manual specifies performing the idle adjustment with the engine oil temperature between 70 - 90 C (158 - 194 F). The factory measuring device uses a probe which inserts into the oil dipstick tube. Since most of us can't justify investing in the factory measuring device, we have to come up with some other method of determining the oil temperature. Personally, I use a contact temperature gauge and measure the temperature on the bottom of the oil pan. If you wish to try the idle adjustment without measuring the oil temperature, run the engine for about 10 minutes after the coolant is at normal operating temperature.
  3. For '85 and newer models defeat the operation of the idle stabilizer by installing the jumper between terminals B and C of the diagnostic plug (see diagram). If you happen to have Special Tool 9246 (Test Relay), it can be used instead of the wire jumper to defeat the idle stabilizer. The idle stabilizer is not operating when the green lamp on the test relay is lit.

  4. Using a flat tip screwdriver or 7mm (9/32") socket, turn the idle speed adjusting screw until the idle speed is within specification for your model vehicle. The tool you need to turn the idle adjustment screw depends on the year and model car you have. For vehicles with automatic transmissions or power steering, adjust to the high idle limit.


    Idle Adjustment Screw - Turbo


    Idle Adjustment Screw - Normally Aspirated

    Vehicle
    Idle Speed (RPM)
    944 (Europe)
    800 + 50
    944 (USA/Canada/Japan)
    900 50
    944 (Australia/Sweden)
    800 + 50
    944 Turbo (All)
    840 40

  5. If you've had trouble with the idle adjustment screw backing out, squeeze a small drop of silicon sealant on top of the idle adjusting screw.

    Clark's Garage 1998