Troubleshooting Troubleshooting – Engine Estimated reading: 5 minutes Contributors Overview This troubleshooting guide is designed to help diagnose and resolve engine starting, running, and lubrication system issues specific to the Porsche 944 S / S2 with the 16v engine (1989–1991). The procedures focus on common problems such as failure to start, rough idling, and oil pressure issues, ensuring compatibility with the S / S2’s advanced fuel injection and ignition systems. Proper diagnosis is critical for maintaining the performance and longevity of your 944 S / S2. Pink and blue text represents links to additional resources, tools, parts, and partner websites. Engine Will Not Rotate This section addresses situations where the engine will not turn over, a straightforward issue with limited causes. Possible Causes Refer To Discharged or Faulty Battery ELECT-15 Battery Terminals Loose or Corroded ELECT-15 Bad Starter Motor or Starter Solenoid ELECT-16 Bad Ignition Switch ELECT-17 Broken or Loose Wiring In Starter Circuit ELECT-17 Broken Teeth on Starter Pinion or Flywheel Remove starter and inspect starter pinion teeth. Roll engine using a 24 mm socket and ratchet to inspect flywheel for broken teeth. Engine Will Rotate But Will Not Start (Fire) When the engine rotates but fails to start, the issue typically stems from a lack of fuel or spark. Use a fuel pressure gauge, spark tester, and digital multimeter for diagnosis. Testing for Lack of Fuel Connect a fuel pressure gauge to the end of the fuel rail. Attempt to start the vehicle while checking the fuel pressure gauge. If the fuel pressure rises, compare the maximum reading to specifications in FUEL-01. If no pressure increase occurs, refer to FUEL-16 for fuel pump troubleshooting. If pressure is low or rises slowly, refer to FUEL-16 for other fuel-related issues. Testing for Lack of Spark Remove the fuel pump fuse to prevent fuel flow during testing. Disconnect a plug wire and connect a spark tester in series with the spark plug. Crank the engine and observe for spark in the tester. If no spark at the plug, disconnect the main lead from the ignition coil to the distributor and test for spark. If spark is present at the coil but not at the plug, replace the distributor cap and/or rotor. If no spark at the coil, proceed with IGN-04 for ignition troubleshooting. Engine Is Difficult to Start When Cold Possible Causes Checks Procedure DME Temperature Sensor Check sensor resistance. ELECT-19 Fuel System Vapor Lock Caused by a bad Fuel Pressure Regulator (FPR), bad fuel pump check valve, or leaking injectors, leading to pressure drop and fuel vaporization. Perform fuel pressure and leakdown test (FUEL-01). If it fails, diagnose with FUEL-17. Fuel Pressure Too High Disconnect one fuel injector connector and attempt to start. If it starts, the FPR is likely faulty. Replace FPR. Note: Car may run rough on three cylinders. Speed/Reference Sensors Wiggle sensor wires/connectors. Clean sensor ends and check clearance. IGN-02 DME Computer Tap DME while attempting to start. Inspect for bad solder joints. DME-05 Engine Is Difficult to Start When Hot Possible Causes Checks Procedure DME/Fuel Pump Relay Test with a jumper during hot start issues. FUEL-05 (Emergency Repairs) Fuel System Vapor Lock Caused by a bad FPR, fuel pump check valve, or leaking injectors. Perform fuel pressure and leakdown test (FUEL-01). If it fails, diagnose with FUEL-17. Speed/Reference Sensors Wiggle sensor wires/connectors. Clean sensor ends and check clearance. IGN-02 DME Computer Tap DME while attempting to start. Inspect for bad solder joints. DME-05 Engine Idles Rough When Cold Possible Causes Checks Procedure DME Temperature Sensor Check cold resistance of the sensor. ELECT-19 Vacuum Leak Inspect hoses downstream of the AFM. N/A Engine Idle Surges Possible Causes Checks Procedure Idle Stabilizer/Auxiliary Air Valve Clamp line to intake manifold. If idle stabilizes, clean or replace the valve. N/A Vacuum Leak Inspect hoses downstream of the AFM. N/A Throttle Body Butterfly Sticking Remove and clean throttle body around butterfly valve. N/A Engine Shudders at Idle Possible Causes Checks Procedure Engine Idle Set Too Low Check and reset idle if necessary. FUEL-08 Engine Hesitates or Stumbles During Acceleration Possible Causes Checks Procedure Dead Spot in Air Flow Meter (AFM) Test AFM. ELECT-19 Vacuum Leak Pressurize intake manifold with 10 psi compressed air and listen for leaks. N/A Spark Plugs Fouled Remove and check spark plug condition. ENG-18 Engine Misses Possible Causes Checks Procedure Bad Spark Plug Wires Run engine in dark and check for arcing. N/A Cracked Distributor Cap Remove and check cap condition. N/A Faulty Spark Plug Inspect spark plugs for damage or wear. ENG-18 Vacuum Leak Pressurize intake manifold and listen for leaks. N/A Clogged Fuel Filter Replace filter. FUEL-03 DME Computer Inspect for bad solder joints. DME-05 Engine Backfires Possible Causes Checks Procedure Faulty Ignition System Check spark plug wires and plugs for faults. N/A Vacuum Leak Pressurize intake manifold and listen for leaks. N/A DME Computer Inspect for bad solder joints. DME-05 Engine Oil Pressure Low Possible Causes Checks/Procedures Oil Level Low Check oil level and top off. Verify low oil level light. LUBE-03 Crankshaft Pulley Bolt Loose Check torque (155 ft-lbs). LUBE-03 Bad Oil Pressure Sending Unit Check sending unit. LUBE-03, ELECT-19 Oil Pump Lost Prime Remove oil filter, pour oil down center hole while turning crankshaft counterclockwise. LUBE-03 Bad or Stuck Open Oil Pressure Relief Valve Remove, clean, and reinstall relief valve. N/A Worn Engine Bearings Check oil pressure when fully warmed up. LUBE-03 Broken Oil Pump Pickup Tube Remove oil pan to inspect (last resort). N/A Bad Oil Pump Remove and inspect pump gears. N/A Engine Oil Pressure High Possible Causes Checks Procedure Bad Oil Pressure Sending Unit Check sending unit. LUBE-03, ELECT-19 Stuck Closed Oil Pressure Relief Valve Remove, clean, and reinstall relief valve. N/A Blocked Oil Passage Check for tapping noise from lifters or oil leaks at cam assembly gasket. N/A Sources Clark’s Garage Pelican Parts Porsche 944 Workshop Manuals YouTube Tagged:EngineEngine Troubleshooting Troubleshooting – Engine - PreviousTroubleshooting – Cooling SystemNext - Troubleshooting – EngineTroubleshooting – Fuel System
