Fuel and Ignition Changing Spark Plugs / Checking the Condition of the Spark Plugs – 2.5L NA Estimated reading: 3 minutes Contributors Overview This procedure outlines how to replace the spark plugs on all Porsche 944 variants with an 8-valve engine and check their condition. Regular spark plug maintenance ensures optimal engine performance, fuel efficiency, and smooth operation. This guide is specific to the 1983–1985.5 (pre-85.5) and 1986–1988 (85.5 onwards) models. No distinctions between pre-85.5 and 85.5 onwards models are noted in the source, so the steps apply to both variants. Pink and blue text represent links to additional resources, tools, parts, and partner websites. Tools Required Spark plug socket (13mm or 1/2 inch) Ratchet (3/8 inch drive) Torque wrench (3/8 inch drive, capable of 25–30 Nm or 18–22 ft-lbs) Feeler gauge (0.7–0.8 mm or 0.028–0.031 inch) Parts Required Spark plugs (Bosch WR7DC or equivalent, 4 required) – 944 602 115 00 Engine oil (small amount for thread lubrication) Step-by-Step Procedure Step 1: Check Spark Plug Gap Measure the gap on each new spark plug using a feeler gauge. The gap should be 0.7–0.8 mm (0.028–0.031 inch). If the gap is incorrect, carefully adjust the side electrode to achieve the specified gap. Note: Bosch spark plugs are typically pre-gapped but should always be verified. Step 2: Prepare New Spark Plugs Apply a light coating of engine oil to the threads of each new spark plug to ease installation and prevent seizing. Step 3: Remove and Replace Spark Plugs Locate the spark plug wires on top of the engine. Work on one spark plug at a time to avoid mixing up the plug wire order. Grasp the spark plug wire boot firmly and twist gently to disconnect it from the first spark plug. Using a spark plug socket and ratchet, remove the old spark plug by turning counterclockwise. Install the new spark plug by hand-threading it clockwise to avoid cross-threading, then tighten using a torque wrench to 25–30 Nm (18–22 ft-lbs). Reconnect the spark plug wire, ensuring the connector is fully seated on the spark plug. Repeat steps 4–8 for the remaining three spark plugs. Step 4: Check Condition of Old Spark Plugs Inspect the removed spark plugs to diagnose engine condition using the following table: Indication Condition / Cause Brown to grayish-brown with minimal electrode wear Normal operation Dry black (carbon) deposits Mixture too rich or weak spark; may cause misfire or hesitation Oily deposits Leaking valve seals or piston oil ring; may cause misfire or hesitation Brown to grayish-brown with obvious electrode wear Spark plugs worn; replace immediately Excessively worn electrode, white insulator, no deposits Mixture too lean or spark plug heat range too hot Heavy tannish deposits Valve guide seal leakage or gasoline additive buildup Post Procedure Checklist Verify all spark plug wires are securely connected and in the correct order. Start the engine and listen for smooth operation, checking for misfires or rough idling. Drive the vehicle for 5 miles (8 km) and recheck for any abnormal engine behavior. Ensure no tools or debris are left in the engine compartment. Sources Clark’s Garage Shop Manual Pelican Parts Technical Articles Porsche 944 Workshop Manual Tagged:Fuel and IgnitionSpark Plugs Changing Spark Plugs / Checking the Condition of the Spark Plugs – 2.5L NA - PreviousAir Flow Meter (AFM) Operation and Testing – 2.5L NANext - Changing Spark Plugs / Checking the Condition of the Spark Plugs – 2.5L NADistributor Cap and Rotor Replacement – 2.5L NA
