Idle Speed Adjustment – 2.5L NA

Overview

This guide outlines the procedure to adjust the idle speed on all Porsche 944 variants with an 8-valve engine, covering pre-1985.5 (1983–1985.5) and 1985.5 onwards (1986–1988) models. Proper idle speed ensures smooth engine operation and prevents stalling. The idle speed adjusting screw may back out over time, requiring adjustment to restore optimal performance.

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Tools Required

• Flat-tip screwdriver
• 7mm (9/32 inch) socket (85.5 Onwards)
• Wire jumper with round male connectors (85.5 Onwards)
• Temperature measuring device (e.g., contact temperature gauge)

Parts Required

• Silicone sealant (optional, 944 606 110 00)

Step-by-Step Procedure

Step 1: Prepare the Vehicle

1. Turn off the fan motor and air conditioning compressor to avoid interference during idle adjustment.
2. Start the engine and let it idle until warm. Aim for an engine oil temperature of 70–90°C (158–194°F).

If you lack a factory oil temperature probe, use a contact temperature gauge on the bottom of the oil pan.
Alternatively, run the engine for about 10 minutes after the coolant reaches normal operating temperature (around 80–90°C or 176–194°F).

Step 2: Disable the Idle Stabilizer (85.5 Onwards)

3. For 85.5 Onwards models:

Locate the diagnostic plug in the engine compartment.
Insert a wire jumper with round male connectors between terminals B and C to disable the idle stabilizer.
Alternatively, if you have Special Tool 9246 (Test Relay), use it instead. The idle stabilizer is disabled when the green lamp on the test relay is lit.

4. For Pre-85.5 models:

No idle stabilizer is present, so skip this step.

Step 3: Adjust the Idle Speed

5. Locate the idle speed adjusting screw on the throttle body (refer to diagrams for normally aspirated engines).

For Pre-85.5 models:
Use a flat-tip screwdriver to turn the idle speed adjusting screw.
For 85.5 Onwards models:
Use a 7mm (9/32 inch) socket or a flat-tip screwdriver to turn the idle speed adjusting screw.

6. Adjust the screw until the idle speed matches the specification for your model:

944 (USA/Canada/Japan): 900 ± 50 RPM.
944 (Europe/Australia/Sweden): 800 ± 50 RPM.
For vehicles with automatic transmissions or power steering, adjust to the higher end of the specified range (e.g., 950 RPM for USA models, 850 RPM for Europe).

Step 4: Secure the Idle Speed Adjusting Screw (Optional)

7. If the idle speed adjusting screw has been backing out, apply a small drop of silicone sealant (944 606 110 00) on top of the screw to secure it.

Ensure the sealant does not interfere with the screw’s threads or throttle body operation.

Post Procedure Checklist

• Verify the idle speed remains within the specified range (800–950 RPM, depending on model) after adjustment.
• Check that the engine runs smoothly without stalling or surging at idle.
• Ensure no tools or debris are left in the engine compartment.
• Confirm the silicone sealant (if used) is properly applied and does not obstruct throttle body components.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manuals
• YouTube