Idle Control Motor (Idle Stabilizer) Replacement -2.5L NA

Overview

This procedure outlines the steps to replace the idle control motor (also known as the idle stabilizer) on all Porsche 944 variants with an 8-valve engine, specifically for models from 1985.5 onwards. The idle control motor regulates engine idle speed by allowing metered air into the intake manifold, ensuring stable idle under various conditions, such as when the engine is cold or under load from accessories like air conditioning. A faulty idle control motor can cause erratic idle, stalling, or air leaks, leading to poor engine performance. This guide is tailored for DIY enthusiasts with mechanical experience and focuses on the 1985.5–1988 Porsche 944 (8-valve engine).

Pink and blue text represent links to additional resources, tools, parts, and partner websites.

Tools Required

• 13mm (1/2 inch) wrench
• Screwdriver (for hose clamps)
• Standard mechanic’s tool set (including pliers and sockets for general use)

Parts Required

• Idle control motor (944 606 103 00)
• Rubber mounts (2) (999 703 139 00)
• Hose clamps (if needed for replacement) (999 512 350 00)

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Fuel Injector Removal
• Intake Manifold Removal
• Allen Head and Cheese Head Removal
• Idle Speed Adjustment

Step-by-Step Procedure

Step 1: Remove the Intake Manifold

1. Follow this link to ensure this step – Intake Manifold Removal – of the process is followed accurately.
2. Inspect all visible hoses, rubber components, and the engine block for wear or damage. Replace any deteriorated parts, such as vacuum lines or coolant hoses, to prevent future failures.
3. Clean the exposed engine block area to remove debris and check for any loose or missing nuts and bolts.

Step 2: Remove the Fuel Rail

4. Follow this link to ensure this step – Fuel Injector Removal – of the process is followed accurately.

Step 3: Loosen the Idle Control Motor

5. Locate the idle control motor mounted on the engine block, near the intake manifold (85.5 Onwards).
6. Using a 13mm (1/2 inch) wrench, loosen the bolt securing the idle control motor to its mounting bracket.

Step 4: Disconnect the Left-Side Hose

7. Locate the hose connected to the intake boot (left side) of the idle control motor.
8. Using a screwdriver, loosen the hose clamp and carefully remove the hose from the idle control motor.

Step 5: Disconnect the Electrical Connector

9. Locate the electrical connector attached to the idle control motor.
10. Gently unplug the electrical connector, checking for any signs of damaged or frayed wiring.

Step 6: Remove the Idle Control Motor

11. Slide the idle control motor out of its mounting bracket, keeping the right-side hose attached for now (85.5 Onwards).

For 85.5 Onwards models with broken rubber mounts:
Remove the bottom section of the broken rubber mounting bolts from the engine block. Follow this link to ensure this step – Allen Head and Cheese Head Removal – of the process is followed accurately.
Install new rubber mounts (999 703 139 00) onto the engine block.
Remove the broken rubber mounting bolts from the mounting bracket and install new ones if necessary.

Step 7: Prepare the New Idle Control Motor

12. Mark the right-side hose (still attached to the old idle control motor) to indicate its orientation for reinstallation.
13. Carefully remove the right-side hose from the old idle control motor and attach it to the new idle control motor (944 606 103 00).
14. Check the arrow on the new idle control motor indicating airflow direction. Ensure it is oriented correctly to match the original setup.

Step 8: Install the New Idle Control Motor

15. Slide the new idle control motor into the mounting bracket while reattaching the left-side hose to the intake boot (85.5 Onwards).
16. Using a screwdriver, tighten the hose clamps on both the left-side and right-side hoses to secure them.
17. Using a 13mm (1/2 inch) wrench, tighten the mounting bracket bolt to secure the idle control motor. Torque to 20 Nm (15 ft-lbs).

For 85.5 Onwards models replacing rubber mounts:
Place the mounting bracket onto the new rubber mounts (999 703 139 00).
Tighten the nuts on the rubber mounts to secure the bracket. Torque to 10 Nm (7.4 ft-lbs).

Step 9: Reattach the Electrical Connector

18. Reconnect the electrical connector to the new idle control motor, ensuring a secure connection.

Step 10: Reinstall the Intake Manifold and Fuel Rail

19. Follow this link to ensure this step – Intake Manifold Removal – of the process is followed accurately to reinstall the intake manifold.
20. Follow this link to ensure this step – Fuel Injector Removal – of the process is followed accurately to reinstall the fuel rail.

Step 11: Test and Adjust Idle Speed

21. Reconnect the battery if it was disconnected during the procedure.
22. Start the engine and let it warm up to operating temperature.
23. Check for any air or vacuum leaks around the idle control motor and hoses. If a leak is suspected, carefully spray a small amount of starting fluid near the suspected area (use extreme caution, as starting fluid is highly flammable). A momentary increase in RPM indicates a leak.
24. Verify that the idle speed is stable, even when the engine is cold.
25. Check the idle speed against the following specifications (85.5 Onwards):

For 944 (US/Canada/Japan): 900 ± 50 RPM
For 944 (Rest of World): 800 ± 50 RPM

26. If the idle speed is outside these ranges, follow this link to ensure this step – Idle Speed Adjustment – of the process is followed accurately.

Post Procedure Checklist

• Verify that the idle speed is stable and within the specified range (900 ± 50 RPM for US/Canada/Japan; 800 ± 50 RPM for Rest of World).
• Check for air or vacuum leaks around the idle control motor, hoses, and intake manifold.
• Ensure all hose clamps are tight and hoses are properly oriented.
• Confirm the electrical connector is securely attached and wiring is undamaged.
• Inspect the engine bay for any tools, debris, or loose components.
• Test drive the vehicle for 5 miles (8 km) to ensure stable idle under various conditions (e.g., cold engine, air conditioning on).

Sources

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