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Home >> Subaru >> 2005 >> Impreza WRX STi >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Engine (Diagnostics) -- H4DOTC >> General Diagnostic Table >> Inspection >> Engine
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General Diagnostic Table: Inspection: Engine

NOTE: Malfunction of parts other than those listed is also possible. < Ref. to ENGINE NOISE . >
ENGINE GENERAL DIAGNOSTIC

Symptom Problem parts
1. Engine stalls during idling.
  1. Idle air control solenoid valve
  2. Manifold absolute pressure sensor
  3. Mass air flow and intake 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. Idle air control solenoid valve
  2. Manifold absolute pressure sensor
  3. Mass air flow and intake temperature sensor
  4. Engine coolant temperature sensor ((2))
  5. Ignition parts ((1))
  6. Air intake system ((5))
  7. Fuel injection parts ((4))
  8. Throttle position sensor
  9. Crankshaft position sensor ((3))
  10. Camshaft position sensor ((3))
  11. Oxygen sensor
  12. Fuel pump and fuel pump relay
3. Engine does not return to idle.
  1. Idle air control solenoid valve
  2. Engine coolant temperature sensor
  3. Accelerator cable ((6))
  4. Throttle position sensor
  5. Manifold absolute pressure sensor
  6. Mass air flow sensor
4. Poor acceleration
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake temperature sensor
  3. Throttle position sensor
  4. Fuel pump and fuel pump relay
  5. Engine coolant temperature sensor ((2))
  6. Crankshaft position sensor ((3))
  7. Camshaft position sensor ((3))
  8. A/C switch and A/C cut relay
  9. Engine torque control signal circuit
  10. Ignition parts ((1))
5. Engine stalls or engine sags or hesitates at acceleration.
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake 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. Throttle position sensor
  9. Fuel pump and fuel pump relay
6. Surge
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake temperature sensor
  3. Engine coolant temperature sensor ((2))
  4. Crankshaft position sensor ((3))
  5. Camshaft position sensor ((3))
  6. Fuel injection parts ((4))
  7. Throttle position sensor
  8. Fuel pump and fuel pump relay
7. Spark knock
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake temperature sensor
  3. Engine coolant temperature sensor
  4. Knock sensor
  5. Fuel injection parts ((4))
  6. Fuel pump and fuel pump relay
8. After-burning in exhaust system
  1. Manifold absolute pressure sensor
  2. Mass air flow and intake 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 ignitor assembly and spark plug.
(2) Indicate the symptom occurring only in cold temperatures.
(3) Ensure the secure installation.
(4) Check fuel injector, fuel pressure regulator and fuel filter.
(5) Inspect air leak in air intake system.
(6) Adjust accelerator cable.
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