Contents Wiring diagrams Section: Mechanical All sections

Engine Mechanical (Sti): Diagnosis Subaru Impreza GH

Mechanical 10 illustrations ~1325 words

INSPECTION

CAUTIONAfter warming-up, engine becomes very hot. Be careful not to burn yourself during measurement.

Scheme 108

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Scheme 109
  1. After warming-up the engine, turn the ignition switch to OFF.
  2. Make sure that the battery is fully charged.
  3. Remove the fuse of fuel pump from main fuse box.
  4. Start the engine and run it until it stalls.
  5. After the engine stalls, crank it for five more seconds.
  6. Turn the ignition switch to OFF.
  7. Remove all spark plugs. Refer to «REMOVAL»(ref-357093-S11160938452010030800000) , Spark Plug.
  8. Fully open the throttle valve.
  9. Check the starter motor for satisfactory performance and operation.
  10. Secure the compression gauge tightly against the spark plug hole. NOTE: When using a screw-in type compression gauge, the screw should be less than 18 mm (0.71 in) long.
  11. Crank the engine by the starter motor, and read the maximum value on the gauge when the needle of compression gauge is steady.
  12. Perform at least two measurements per cylinder, and make sure that the values are correct. Compression (fully open throttle): Standard 981 - 1,177 kPa (10 - 12 kgf/cm 2 , 142 - 171 psi) Difference between cylinders 49 kPa (0.5 kgf/cm 2 , 7 psi) or less
  13. After inspection, install the related parts in the reverse order of removal.
  1. Before checking the idle speed, check the following item: Check the air cleaner element is free from clogging, ignition timing is correct, spark plugs are in good condition, and hoses are connected properly. Check the malfunction indicator light does not illuminate.
  2. Warm up the engine.
  3. Read the engine idle speed using Subaru Select Monitor. Refer to «READ CURRENT DATA FOR ENGINE (NORMAL MODE)»(ref-357088-S16053884052010030800000) , OPERATION, Subaru Select Monitor.
  4. Check the idle speed when no-loaded. (Headlight, heater fan, rear defroster, radiator fan, A/C and etc. are OFF) Idle speed (No load and gear shift lever in neutral position): 700±100 RPM
  5. Check the idle speed when loaded. (Turn the A/C switch to "ON" and operate the compressor for at least one minute before measurement.) Idle speed (A/C ON and gear shift lever in neutral position): 750±100 RPM NOTE: Idle speed cannot be adjusted manually, because the idle speed is automatically adjusted. If the prescribed idle speed cannot be maintained, refer to «BASIC DIAGNOSTIC PROCEDURE»(ref-357088-S11463676542010030800000) , General On-board Diagnosis Table.
CAUTIONAfter warming-up, engine becomes very hot. Be careful not to burn yourself at measurement.
CAUTIONBefore removing the fuel pressure gauge, release the fuel pressure. Be careful not to spill fuel. Catch the fuel from hoses using a container or cloth.

Note. If the fuel pressure is out of specification, check or replace the pressure regulator and pressure regulator vacuum hose.

Scheme 110

Scheme 110
  1. Release the fuel pressure. Refer to «RELEASING OF FUEL PRESSURE»(ref-357081-S28704346012010030800000) , PROCEDURE, Fuel.
  2. Open the fuel filler lid and remove the fuel filler cap.
  3. Disconnect the fuel delivery hose from pulsation damper, and connect fuel pressure gauge.
  4. Start the engine.
  5. Measure the fuel pressure while disconnecting pressure regulator vacuum hose from intake manifold. NOTE: The fuel pressure gauge registers 10 to 20 kPa (0.1 to 0.2 kgf/cm 2 , 1 to 3 psi) higher than standard values during high-altitude operations. Fuel pressure: Standard 284 - 3/4 kPa (2.9 - 3.2 kgf/cm 2 , 41 - 46 psi)
  6. After connecting the pressure regulator vacuum hose, measure the fuel pressure. NOTE: The fuel pressure gauge registers 10 to 20 kPa (0.1 to 0.2 kgf/cm 2 , 1 to 3 psi) higher than standard values during high-altitude operations. Fuel pressure: Standard 230 - 260 kPa (2.35 - 2.65 kgf/cm 2 , 33 - 38 psi)
CAUTIONIf engine oil is split onto the exhaust pipe, wipe it off with cloth to avoid emission of smoke or causing a fire.

Note. Inspection and adjustment of valve clearance should be performed while engine is cold.

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Scheme 116

Scheme 116
  1. Set the vehicle on a lift.
  2. Disconnect the ground cable from battery.
  3. Remove the air intake duct. Refer to «REMOVAL»(ref-357076-S39226648372010030800000) , Air Intake Duct.
  4. Remove the bolt which secures timing belt cover RH.
  5. Lift up the vehicle.
  6. Remove the under cover.
  7. Loosen the remaining bolts which secure timing belt cover RH, then remove the timing belt cover.
  8. Lower the vehicle.
  9. When inspecting #1 and #3 cylinders Remove the air cleaner case. Refer to «REMOVAL»(ref-357076-S26446360742010030800000) , Air Cleaner Case. Remove the ignition coil. Refer to «REMOVAL»(ref-357093-S04223111392010030800000) , Ignition Coil. Place a suitable container under the vehicle. Disconnect the PCV hose from the rocker cover RH. NOTE: For the PCV hose affixed with the clamp, fit the depression in the ST with the protrusion of the clamp as shown in the figure below, unlock the clamp and disconnect. ST 18353AA000 CLAMP PLIERS Remove the bolts, then remove the rocker cover RH.
  10. When inspecting #2 and #4 cylinders Remove the battery. Refer to «REMOVAL»(ref-357077-S20111493982010030800000) , Battery. Remove the secondary air pump. Refer to «REMOVAL»(ref-357078-S11886107782010030800000) , Secondary Air Pump. Remove the ignition coil. Refer to «REMOVAL»(ref-357093-S04223111392010030800000) , Ignition Coil. Place a suitable container under the vehicle. Disconnect the PCV hose from the rocker cover LH. NOTE: For the PCV hose affixed with the clamp, fit the depression in the ST with the protrusion of the clamp as shown in the figure below, unlock the clamp and disconnect. ST 18353AA000 CLAMP PLIERS Remove the bolts, then remove the rocker cover LH.
  11. Turn the crank pulley clockwise until the round mark on the camshaft sprocket is set to position shown in the figure. NOTE: Turn the crank pulley using a socket wrench. Measurement of clearance of #1 cylinder intake valve and #3 cylinder exhaust valve Measurement of clearance of #2 cylinder exhaust valve and #3 cylinder intake valve Measurement of clearance of #2 cylinder intake valve and #4 cylinder exhaust valve Measurement of clearance of #1 cylinder exhaust valve and #4 cylinder intake valve
  12. Measure the clearance of intake valve and exhaust valve using thickness gauge (A). NOTE: Insert a thickness gauge in a direction as horizontal as possible with respect to the valve lifter. Lift up the vehicle, and then measure the exhaust valve clearances. If the measured value is not within the inspection value, take notes of the value in order to adjust the valve clearance later on. Valve clearance (inspection value): Intake 0.20 +004 -0.06 mm (0.0079 +0.0016 -0.0024 in) Exhaust 0.35±0.05 mm (0.0138±0.0020 in)
  13. If necessary, adjust the valve clearance. Refer to «ADJUSTMENT»(ref-357079-S30038380442010030800000) , Valve Clearance.
  14. After inspection, install the related parts in the reverse order of removal. NOTE: Use a new rocker cover gasket. Use a new clamp for the PCV hose clamp, fit the cut out in the ST with the protrusion on the clamp as shown in the figure, and lock the clamp. ST 18353AA000 CLAMP PLIERS
  1. Check that pipes, hoses, connectors and clamps are installed firmly.
  2. Check the engine coolant is at specified level.
  3. Start the engine and check for exhaust gas, engine coolant, leaks of fuel, etc. Also check for noise and vibrations.

Make sure that no crack or other damages do not exist.

Scheme 117

Scheme 117: PROCEDURE
  1. After removing the engine from body, install ST to engine as shown in the figure. ST1 498457000 ENGINE STAND ADAPTER RH ST2 498457100 ENGINE STAND ADAPTER LH ST3 499817100 ENGINE STAND
  2. In this information the procedures described under each index are all connected and stated in order. The procedure for overhauling of the engine will be completed when you go through all steps in the process. Therefore, in this service information, to conduct the particular procedure within the flow of a section, you need to go back and conduct the procedure described previously in order to do that particular procedure.
  1. Make sure the V-belt is not worn or otherwise damaged.
  2. Check the tension of the front side belt. Refer to «INSPECTION»(ref-357079-S34100908282010030800000) , V-belt.

Check the timing belt cover for damage.

  1. Check the cam sprocket teeth for abnormal wear and scratches.
  2. Make sure there is no free play between cam sprocket and key.
  1. Check the crank sprocket teeth for abnormal wear and scratches.
  2. Make sure there is no free play between crank sprocket and key.
  3. Check the crank sprocket protrusion used for sensor for damage and contamination of foreign matter.

Note. The "RANK" shown in the chart shows the possibilities of the cause of trouble in order from "Very often" to "Rarely".

A - Very often

B - Sometimes

C - Rarely

SymptomProblem parts etc.Possible causeRANK
1. Engine does not start.
1) Starter does not turn.StarterDefective battery-to-starter harnessB
Defective starter switchC
Defective starterB
BatteryImproper connection of terminalA
Run-down batteryA
Defective charging systemB
FrictionSeizure of crankshaft and connecting rod bearingC
Seized camshaftC
Seized or stuck piston and cylinderC
2) Initial combustion does not occur.StarterDefective starterC
Engine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Fuel lineDefective fuel pump and relayA
Clogged fuel lineC
Lack of fuel or insufficient fuelB
Timing beltDegradation, etc.B
Defective timingB
CompressionIncorrect valve clearanceC
Loosened spark plug or defective gasketC
Loosened cylinder head bolt or defective cylinder head gasketC
Improper valve sealingC
Defective valve stemC
Worn or broken valve springB
Worn or stuck piston rings, cylinder and pistonC
Incorrect valve timingB
Improper engine oil (low viscosity)B
3) Initial combustion occurs.Engine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemDefective intake manifold gasketB
Defective throttle body gasketB
Fuel lineDefective fuel pump and relayC
Clogged fuel lineC
Lack of fuel or insufficient fuelB
Timing beltDegradation, etc.B
Defective timingB
CompressionIncorrect valve clearanceC
Loosened spark plug or defective gasketC
Loosened cylinder head bolt or defective cylinder head gasketC
Improper valve sealingC
Defective valve stemC
Worn or broken valve springB
Worn or stuck piston rings, cylinder and pistonC
Incorrect valve timingB
Improper engine oil (low viscosity)B
4) Engine stalls after initial combustion.Engine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemLoosened or cracked intake ductB
Loosened or cracked PCV hoseC
Loosened or cracked vacuum hoseC
Defective intake manifold gasketB
Defective throttle body gasketB
Dirty air cleaner elementC
Fuel lineClogged fuel lineC
Lack of fuel or insufficient fuelB
Timing beltDegradation, etc.B
Defective timingB
CompressionIncorrect valve clearanceC
Loosened spark plug or defective gasketC
Loosened cylinder head bolt or defective cylinder head gasketC
Improper valve sealingC
Defective valve stemC
Worn or broken valve springB
Worn or stuck piston rings, cylinder and pistonC
Incorrect valve timingB
Improper engine oil (low viscosity)B
2. Rough idle and engine stallEngine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemLoosened or cracked intake ductA
Loosened or cracked PCV hoseA
Loosened or cracked vacuum hoseA
Defective intake manifold gasketB
Defective throttle body gasketB
Defective PCV valveC
Loosened oil filler capB
Dirty air cleaner elementC
Fuel lineDefective fuel pump and relayC
Clogged fuel lineC
Lack of fuel or insufficient fuelB
Timing beltDefective timingC
CompressionIncorrect valve clearanceB
Loosened spark plug or defective gasketB
Loosened cylinder head bolt or defective cylinder head gasketB
Improper valve sealingB
Defective valve stemC
Worn or broken valve springB
Worn or stuck piston rings, cylinder and pistonB
Incorrect valve timingA
Improper engine oil (low viscosity)B
Lubrication systemIncorrect oil pressureB
Defective rocker cover gasketC
Cooling systemOver-heatingC
OthersEvaporative emission control system malfunctionA
Stuck or damaged throttle valveB
3. Low output, hesitation and poor accelerationEngine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemLoosened or cracked intake ductA
Loosened or cracked PCV hoseA
Loosened or cracked vacuum hoseB
Defective intake manifold gasketB
Defective throttle body gasketB
Defective PCV valveB
Loosened oil filler capB
Dirty air cleaner elementA
Fuel lineDefective fuel pump and relayB
Clogged fuel lineB
Lack of fuel or insufficient fuelC
Timing beltDefective timingB
CompressionIncorrect valve clearanceB
Loosened spark plug or defective gasketB
Loosened cylinder head bolt or defective cylinder head gasketB
Improper valve sealingB
Defective valve stemC
Worn or broken valve springB
Worn or stuck piston rings, cylinder and pistonC
Incorrect valve timingA
Improper engine oil (low viscosity)B
Lubrication systemIncorrect oil pressureB
Cooling systemOver-heatingC
Over-coolingC
OthersEvaporative emission control system malfunctionA
4. SurgingEngine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemLoosened or cracked intake ductA
Loosened or cracked PCV hoseA
Loosened or cracked vacuum hoseA
Defective intake manifold gasketB
Defective throttle body gasketB
Defective PCV valveB
Loosened oil filler capB
Dirty air cleaner elementB
Fuel lineDefective fuel pump and relayB
Clogged fuel lineB
Lack of fuel or insufficient fuelC
Timing beltDefective timingB
CompressionIncorrect valve clearanceB
Loosened spark plug or defective gasketC
Loosened cylinder head bolt or defective cylinder head gasketC
Improper valve sealingC
Defective valve stemC
Worn or broken valve springC
Worn or stuck piston rings, cylinder and pistonC
Incorrect valve timingA
Improper engine oil (low viscosity)B
Cooling systemOver-heatingB
OthersEvaporative emission control system malfunctionC
5. Engine does not return to idle.Engine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemLoosened or cracked vacuum hoseA
OthersStuck or damaged throttle valveA
6. Dieseling (Run-on)Engine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Cooling systemOver-heatingB
OthersEvaporative emission control system malfunctionB
7. After burning in exhaust systemEngine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemLoosened or cracked intake ductC
Loosened or cracked PCV hoseC
Loosened or cracked vacuum hoseB
Defective PCV valveB
Loosened oil filler capC
Timing beltDefective timingB
CompressionIncorrect valve clearanceB
Loosened spark plug or defective gasketC
Loosened cylinder head bolt or defective cylinder head gasketC
Improper valve sealingB
Defective valve stemC
Worn or broken valve springC
Worn or stuck piston rings, cylinder and pistonC
Incorrect valve timingA
Lubrication systemIncorrect oil pressureC
Cooling systemOver-coolingC
OthersEvaporative emission control system malfunctionC
8. KnockingEngine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemLoosened oil filler capB
Timing beltDefective timingB
CompressionIncorrect valve clearanceC
Incorrect valve timingB
Cooling systemOver-heatingA
9. Excessive engine oil consumptionIntake systemLoosened or cracked PCV hoseA
Defective PCV valveB
Loosened oil filler capC
CompressionDefective valve stemA
Worn or stuck piston rings, cylinder and pistonA
Lubrication systemLoosened oil pump attaching bolts and defective gasketB
Defective oil filter gasketB
Defective crankshaft oil sealB
Defective rocker cover gasketB
Loosened oil drain plug or defective gasketB
Loosened oil pan fitting bolts or defective oil panB
10. Excessive fuel consumptionEngine control system Refer to BASIC DIAGNOSTIC PROCEDURE .A
Intake systemDirty air cleaner elementA
Timing beltDefective timingB
CompressionIncorrect valve clearanceB
Loosened spark plug or defective gasketC
Loosened cylinder head bolt or defective cylinder head gasketC
Improper valve sealingB
Defective valve stemC
Worn or broken valve springC
Worn or stuck piston rings, cylinder and pistonB
Incorrect valve timingB
Lubrication systemIncorrect oil pressureC
Cooling systemOver-coolingC

PROBLEM SYMPTOM REFERENCE CHART

Type of soundConditionPossible cause
Regular clicking soundSound increases as engine speed increases.Valve mechanism is defective. Incorrect valve clearance Worn camshaft Broken valve spring
Heavy and dull clankOil pressure is low.Worn crankshaft main bearing Worn connecting rod bearing (large end)
Oil pressure is normal.Loosened flywheel mounting bolt Damaged engine mounting
High-pitched clankSound is noticeable when accelerating with an overload condition.Ignition timing advanced Accumulation of carbon inside combustion chamber Wrong heat range of spark plug Improper octane value gasoline
Clank when engine speed is between 1,000 and 2,000 rpms.Noise is reduced when fuel injector connector of noisy cylinder is disconnected. ( (1) )Worn crankshaft main bearing Worn connecting rod bearing (large end)
Knocking sound when engine is operating under idling speed and engine is warmNoise is reduced when fuel injector connector of noisy cylinder is disconnected. ( (1) )Worn cylinder liner and piston ring Broken or stuck piston ring Worn piston pin and hole at piston end of connecting rod
Sound is not reduced if each fuel injector connector is disconnected in turn. ( (1) )Unusually worn valve lifter Worn cam sprocket Worn camshaft journal bore in cylinder head
Squeaky soundInsufficient generator lubrication
Rubbing soundPoor contact of generator brush and rotor
Gear scream when starting engineDefective ignition starter switch Worn gear and starter pinion
Sound like polishing glass with a dry clothLoose V-belt Defective water pump shaft
Hissing soundInsufficient compression Air leakage in air intake system, hose, connection or manifold
Timing belt noiseLoose timing belt Timing belt contacting with adjacent part
Valve noiseIncorrect valve clearance
(1) When disconnecting the fuel injector connector, the malfunction indicator light illuminates and DTC is stored in ECM memory. Therefore, perform the Clear Memory Mode Refer to OPERATION , Clear Memory Mode. and Inspection Mode Refer to PROCEDURE , Inspection Mode. after connecting the fuel injector connector.
(1)When disconnecting the fuel injector connector, the malfunction indicator light illuminates and DTC is stored in ECM memory. Therefore, perform the Clear Memory Mode Refer to OPERATION , Clear Memory Mode. and Inspection Mode Refer to PROCEDURE , Inspection Mode. after connecting the fuel injector connector.

ENGINE NOISE AND POSSIBLE CAUSE REFERENCE CHART