2016 Subaru WRX BaseFACTORY OEM SERVICE PROCEDURE

General Diagnostic Table: Inspection: Engine

NOTE: Malfunction of parts other than those listed is also possible. < Ref. to ENGINE TROUBLE IN GENERAL . >
Symptoms Faulty parts
1. Engine stalls during idling.
  1. Electronic throttle control
  2. Manifold absolute pressure sensor
  3. Mass air flow and intake air temperature sensor
  4. Ignition parts ((1))
  5. Engine coolant temperature sensor ((2))
  6. Crankshaft position sensor ((3))
  7. Camshaft position sensor ((3))
  8. Fuel injection parts ((4))
2. Rough idling
  1. Electronic throttle control
  2. Manifold absolute pressure sensor
  3. Mass air flow and intake air temperature sensor
  4. Engine coolant temperature sensor ((2))
  5. Ignition parts ((1))
  6. Air intake system ((5))
  7. Fuel injection parts ((4))
  8. Crankshaft position sensor ((3))
  9. Camshaft position sensor ((3))
  10. Oxygen sensor
  11. Fuel pump and fuel pump relay
  12. EGR control valve
3. Engine does not return to idle.
  1. Electronic throttle control
  2. Engine coolant temperature sensor
  3. Manifold absolute pressure sensor
  4. Mass air flow and intake air temperature sensor
  5. Accelerator pedal position sensor
  6. EGR control valve
  7. Engine oil temperature sensor
4. Poor acceleration
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake air temperature sensor
  3. Electronic throttle control
  4. Fuel injection parts ((4))
  5. Fuel pump and fuel pump relay
  6. Engine coolant temperature sensor ((2))
  7. Crankshaft position sensor ((3))
  8. Camshaft position sensor ((3))
  9. Accelerator pedal position sensor
  10. Engine torque control signal circuit
  11. Ignition parts ((1))
  12. EGR control valve
  13. Engine oil temperature sensor
5. Engine stalls, hesitates, or sputters at acceleration.
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake air temperature sensor
  3. Engine coolant temperature sensor ((2))
  4. Crankshaft position sensor ((3))
  5. Camshaft position sensor ((3))
  6. Purge control solenoid valve
  7. Fuel injection parts ((4))
  8. Fuel pump and fuel pump relay
  9. Electronic throttle control
  10. EGR control valve
6. Surging
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake air temperature sensor
  3. Engine coolant temperature sensor ((2))
  4. Crankshaft position sensor ((3))
  5. Camshaft position sensor ((3))
  6. Fuel injection parts ((4))
  7. Electronic throttle control
  8. Fuel pump and fuel pump relay
  9. EGR control valve
7. Spark knock
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake air temperature sensor
  3. Engine coolant temperature sensor
  4. Knock sensor
  5. Fuel injection parts ((4))
  6. Fuel pump and fuel pump relay
  7. EGR control valve
8. After burning in exhaust system
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake air temperature sensor
  3. Engine coolant temperature sensor ((2))
  4. Fuel injection parts ((4))
  5. Fuel pump and fuel pump relay
(1) Check ignition coil and spark plug.
(2) Indicate the symptom occurring only in cold temperatures.
(3) Ensure secure installation.
(4) Check fuel injector, fuel pressure regulator and fuel filter.
(5) Inspect for air leak in air intake system.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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