Engine Mechanical (H4DOTC) (Except Sti): Diagnosis Subaru Impreza GH

INSPECTION

Scheme 600

Scheme 601

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. Ref. to «REMOVAL»(ref-357271-S39037743382010031100000) , 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. Ref. to «READ CURRENT DATA FOR ENGINE (NORMAL MODE)»(ref-357262-S36139671992010031100000) , 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 at "P" or "N" position on AT model, or neutral position on MT model): 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 at "P" or "N" position on AT model, or neutral position on MT model)

825±100 RPM (AT model)

800±100 RPM (MT model)

Note. Idle speed cannot be adjusted manually, because the idle speed is automatically adjusted. If the prescribed idle speed cannot be maintained, the General On-board Diagnosis Table under "Engine Control System". Ref. to BASIC DIAGNOSTIC PROCEDURE .

1. Warm up the engine.
2. Remove the intercooler. Ref. to «REMOVAL»(ref-357235-S29312200482010031100000) , Intercooler.
3. Disconnect the brake booster vacuum hose from the intake manifold, and install the vacuum gauge.
4. Install the intercooler. Ref. to «INSTALLATION»(ref-357235-S05398122832010031100000) , Intercooler.
5. Keep the engine at idle speed and read the vacuum gauge indication.

By observing the vacuum gauge needle movement, the internal condition of the engine can be diagnosed as described below.

Scheme 602

Intake manifold vacuum (at idling, A/C OFF)

Less than -68.0 kPa (-510 mmHg, -20.08 inHg) (AT model)

Less than -70.6 kPa

(-530 mmHg, -20.85 inHg) (MT model)

INTAKE MANIFOLD VACUUM REFERENCE

Scheme 603

1. Disconnect the ground cable from battery.
2. Remove the oil pressure switch. Ref. to «REMOVAL»(ref-357256-S11152351472010031100000) , Oil Pressure Switch.
3. Install the oil pressure gauge to cylinder block.
4. Connect the ground cable to battery.
5. Start the engine, and measure the oil pressure. Engine oil pressure: Standard 98 kPa (1.0 kgf/cm 2 , 14 psi) or more (at 600 RPM) 294 kPa (3.0 kgf/cm 2 , 43 psi) or more (at 5,000 RPM) If the oil pressure is out of specification, check oil pump, oil filter and lubrication line. Ref. to «INSPECTION»(ref-357256-S20589729492010031100000) , Engine Lubrication System Trouble in General. If the oil pressure warning light is ON and oil pressure is within specification, check the oil pressure switch. Ref. to «INSPECTION»(ref-357256-S20589729492010031100000) , Engine Lubrication System Trouble in General. NOTE: Standard value is based on an engine oil temperature of 80°C (176°F).
6. After measuring the oil pressure, install the oil pressure switch. Ref. to «INSTALLATION»(ref-357256-S24709454472010031100000) , Oil Pressure Switch.

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

Scheme 604

1. Release the fuel pressure. Ref. to «RELEASING OF FUEL PRESSURE»(ref-357241-S05249623012010031100000) , PROCEDURE, Fuel.
2. Open the fuel filler lid and remove the fuel filler cap.
3. Disconnect the fuel delivery hose from fuel 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 - 314 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)

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

Scheme 605

Scheme 606

Scheme 607

Scheme 608

Scheme 609

Scheme 610

1. Set the vehicle on a lift.
2. Disconnect the ground cable from battery.
3. Remove the air intake duct. Ref. to «REMOVAL»(ref-357235-S10313590332010031100000) , 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. Ref. to «REMOVAL»(ref-357235-S04762520242010031100000) , Air Cleaner Case. Remove the ignition coil. Ref. to «REMOVAL»(ref-357271-S34847988102010031100000) , 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. Ref. to «REMOVAL»(ref-357234-S21509179942010031100000) , Battery. Remove the secondary air pump. Ref. to «REMOVAL»(ref-357270-S12317452782010031100000) , Secondary Air Pump. Remove the ignition coil. Ref. to «REMOVAL»(ref-357271-S34847988102010031100000) , 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 and arrow mark on the cam sprocket are 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 +00016 -0.0024 in) Exhaust 0.35±0.05 mm (0.0138±0.0020 in)
13. If necessary, adjust the valve clearance. Ref. to «ADJUSTMENT»(ref-357237-S00702231282010031100000) , 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. Check that the ATF is at specified level. (AT model)
4. 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 611

1. After removing the engine from body, secure it to ST in the following procedure. ST1 498457000 ENGINE STAND ADAPTER RH ST2 498457100 ENGINE STAND ADAPTER LH ST3 499817100 ENGINE STAND
2. In this article 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 article, to conduct the particular procedure within the flow of a article, 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. Ref. to «INSPECTION»(ref-357237-S00231659292010031100000) , 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

SYMPTOM CHART

POSSIBLE CAUSE REFERENCE