Mitsubishi 380. Manual — part 752

ON-VEHICLE SERVICE

TSB Revision

ENGINE MECHANICAL <3.8L ENGINE>

11A-10

COMPRESSION PRESSURE CHECK

M1111002601112

Required Special Tool:
: Diagnostic Tool (MUT-III)
1. Before inspection, check that the engine oil, starter and

battery are normal. Also, set the vehicle in the following
condition:

• Engine coolant temperature: 80 − 95°C (176 − 203°F)

• Lights and all accessories: OFF

• Transmission: P range

2. Remove all of the ignition coils and spark plugs.
3. Disconnect the crankshaft position sensor connector.

NOTE: Doing this will prevent the engine control unit from
carrying out ignition and fuel injection.

WARNING

Keep your distance from the spark plug hole when
cranking. Oil, fuel, etc., may spray out from the spark
plug hole and may cause serious injury.

4. Cover the spark plug hole with a shop towel etc., during

cranking. After the engine has been cranked, check for
foreign material adhering to the shop towel.

5. Set compression gauge to one of the spark plug holes.

6. Crank the engine with the throttle valve fully open and

measure the compression pressure.

Standard value (at engine speed of 200 r/min): 1,550
kPa (225 psi)

Minimum limit (at engine speed of 200 r/min): 1,110
kPa (161 psi)

7. Measure the compression pressure for all the cylinders, and

check that the pressure differences of the cylinders are
below the limit.

Limit: 98 kPa (14 psi)

8. If there is a cylinder with compression or a compression

difference that is outside the limit, pour a small amount of
engine oil through the spark plug hole, and repeat the
operations in steps 6 to 8.

(1) If the compression increases after oil is added, the cause

of the malfunction is a worn or damaged piston ring
and/or cylinder inner surface.

(2) If the compression does not rise after oil is added, the

cause is a burnt or defective valve seat, or pressure is
leaking from the gasket.

9. Connect the crankshaft position sensor connector.

10.Install the spark plugs and ignition coils.

AK303010

CRANKSHAFT

POSITION SENSOR

CONNECTOR

AB

AKX00436

COMPRESSION

GAUGE

AB

ON-VEHICLE SERVICE

TSB Revision

ENGINE MECHANICAL <3.8L ENGINE>

11A-11

11.Use the Diagnostic Tool (MUT-III) to erase the diagnostic

trouble codes.

NOTE: This will erase the diagnostic trouble code resulting
from the crankshaft position sensor connector being discon-
nected.

MANIFOLD VACUUM CHECK

M1111002700848

1. Start the engine and allow it to warm up until the

temperature of the engine coolant reaches 80

− 95°C (176 −

203

°F).

2. Connect an engine tachometer.
3. Disconnect the ventilation hose from the positive crankcase

ventilation (PCV) valve, and connect a vacuum gauge to the
ventilation hose.

4. Plug the PCV valve.

5. Start the engine and check that idle speed is within

specification. Then check the vacuum gauge reading.

Idle speed: 680

± 100 r/min

Minimum limit: 60 kPa (18 in Hg)

LASH ADJUSTER CHECK

M1111002900400

If an abnormal noise (chattering noise) suspected to be caused
by malfunction of the lash adjuster is produced immediately
after starting the engine and does not disappear, perform the
following check.

NOTE: An abnormal noise due to malfunction of the lash
adjuster is produced immediately after starting the engine and
changes with the engine speed, irrespective of the engine load.
If, the abnormal noise is not produced immediately after start-
ing the engine or does not change with the engine speed, or it
changes with the engine load, the lash adjuster is not the cause
for the abnormal noise.

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AK301335AB

VACUUM

GAUGE

POSITIVE CRANKCASE

VENTILATION VALVE

VENTILATION HOSE
PLUG

ON-VEHICLE SERVICE

TSB Revision

ENGINE MECHANICAL <3.8L ENGINE>

11A-12

NOTE: When the lash adjuster is malfunctioning, the abnormal
noise is rarely eliminated by continuing the warming-up of the
engine at idle speed.
However, the abnormal noise may disappear only when seizure
is caused by oil sludge in the engine whose oil is not main-
tained properly.
1. Start the engine.

2. Check if the abnormal noise produced immediately after

starting the engine, changes with the change in the engine
speed.
If the abnormal noise is not produced immediately after
starting the engine or it does not change with the engine
speed, the lash adjuster is not the cause for the noise.
Therefore, investigate other causes. The abnormal noise is
probably caused by some other parts than the engine proper
if it does not change with the engine speed. (In this case, the
lash adjuster is in good condition.)

3. With the engine idling, change the engine load (shift from N

to D range, for example) to make sure that there is no
change in the level of abnormal noise.
If there is a change in the level of abnormal noise, suspect a
tapping noise due to worn crankshaft bearing or connecting
rod bearing (In this case, the lash adjuster is in good
condition.).

4. After completion of warm-up, run the engine at idle to check

for abnormal noise.
If the noise is reduced or disappears, clean the lash adjuster
(Refer to GROUP 11B, Engine Overhaul

− Rocker Arms

and Camshaft

− Inspection

P.11B-23

). As it is suspected

that the noise is due to seizure of the lash adjuster. If there is
no change in the level of the abnormal noise, proceed to
step 5.

5. Run the engine to bleed the lash adjuster system (Refer to

P.11A-11

.).

6. If the abnormal noise does not disappear after air bleeding

operation, clean the lash adjuster (Refer to GROUP 11B,
Engine Overhaul

− Rocker Arms and Camshaft − Inspection

P.11B-23

).

.

Bleeding lash adjuster system

NOTE: Parking the vehicle on a grade for a long time may
decrease oil in the lash adjuster, causing air to enter the high
pressure chamber when starting the engine.

NOTE: After parking for many hours, oil may run out from the
oil passage and take time before oil is supplied to the lash
adjuster, causing air to enter the high pressure chamber.

NOTE: In the above cases, abnormal noise can be eliminated
by bleeding the lash adjuster system.

ON-VEHICLE SERVICE

TSB Revision

ENGINE MECHANICAL <3.8L ENGINE>

11A-13

1. Check engine oil and add or change oil if required.

NOTE: If the engine oil level is low, air is sucked from the oil
screen, causing air to enter the oil passage.

NOTE: If the engine oil level is higher than specification, oil
may be stirred by the crankshaft, causing oil to be mixed
with a large quantity of air.

NOTE: If oil is deteriorated, air is not easily separated from
oil, increasing the quantity of air contained in oil.

NOTE: If air mixed with oil enters the high pressure chamber
inside the lash adjuster from the above causes, air in the
high pressure chamber is compressed excessively while the
valve is opened, resulting in an abnormal noise when the
valve closes. This is the same phenomenon as that
observed when the valve clearance has become excessive.
The lash adjuster can resume normal function when air
entered the lash adjuster is removed.

2. Idle the engine for one to three minutes to warm it up.
3. Repeat the operation pattern, shown in left figure, at no load

to check for abnormal noise. (Usually the abnormal noise is
eliminated after repetition of the operation 10 to 30 times. If,
however, no change is observed in the level of abnormal
noise after repeating the operation more than 30 times,
suspect that the abnormal noise is due to some other
factors.)

4. After elimination of abnormal noise, repeat the operation

shown in left figure five more times.

5. Run the engine at idle for one to three minutes to make sure

that the abnormal noise has been eliminated.

AKX00328

GOOD

MINIMUM

MAXIMUM

AB

AKX00329

HIGH-

PRESSURE

CHAMBER

AB

AKX00330

OPEN THROTTLE

VALVE GRADUALLY

CLOSE

THROTTLE VALVE

APPROXI-

MATELY

3,000 r/min

IDLING

OPERATION

ONCE

15 s

15 s

AIR BLEEDING OPERATION PATTERN

AB