(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING) - PERFORMANCE and (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)—MECHANICAL for possible causes and corrections of malfunctions. (Refer to 14 - FUEL SYSTEM/
FUEL DELIVERY - DIAGNOSIS AND TESTING) and (Refer to 14 - FUEL SYSTEM/FUEL INJECTION - DIAGNO-
SIS AND TESTING) for the fuel system diagnosis.

Additional tests and diagnostic procedures may be necessary for specific engine malfunctions that can not be iso-
lated with the Service Diagnosis charts. Information concerning additional tests and diagnosis is provided within the
following diagnosis:

•

Cylinder Compression Pressure Test (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

•

Cylinder Combustion Pressure Leakage Test (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

•

Engine Cylinder Head Gasket Failure Diagnosis (Refer to 9 - ENGINE/CYLINDER HEAD - DIAGNOSIS AND
TESTING).

•

Intake Manifold Leakage Diagnosis (Refer to 9 - ENGINE/MANIFOLDS/INTAKE MANIFOLD - DIAGNOSIS
AND TESTING).

DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - PERFORMANCE

CONDITION

POSSIBLE CAUSE

CORRECTION

ENGINE WILL NOT START

1. Weak battery

1. Charge or replace as necessary.

2. Corroded or loose battery
connections.

2. Clean and tighten battery
connections. Apply a coat of light
mineral grease to the terminals.

3. Faulty starter.

3. (Refer to 8 - ELECTRICAL/
STARTING - DIAGNOSIS AND
TESTING).

4. Faulty coil or control unit.

4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

5. Incorrect spark plug gap.

5. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).

6. Dirt or water in fuel system.

6. Clean system and replace fuel
filter.

7. Faulty fuel pump, relay or wiring.

7. Repair or replace as necessary.

9 - 1192

ENGINE - 4.7L SERVICE INFORMATION

CONDITION

POSSIBLE CAUSE

CORRECTION

ENGINE STALLS OR ROUGH IDLE

1. Idle speed set to low.

1. (Refer to 14 - FUEL SYSTEM/
FUEL INJECTION/IDLE AIR
CONTROL MOTOR - REMOVAL).

2. Idle mixture too lean or too rich.

2. Refer to Powertrain Diagnosis
Information.

3. Vacuum leak.

3. Inspect intake manifold and
vacuum hoses, repair or replace as
necessary.

4. Faulty coil.

4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

5. Incorrect engine timing.

5. (Refer to 9 - ENGINE/VALVE
TIMING - STANDARD
PROCEDURE).

ENGINE LOSS OF POWER

1. Dirty or incorrectly gapped spark
plugs.

1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).

2. Dirt or water in fuel system.

2. Clean system and replace fuel
filter.

3. Faulty fuel pump.

3. Refer to the Appropriate
Diagnostic Information

4. Blown cylinder head gasket.

4. Replace cylinder head gasket.

5. Low compression.

5. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).

6. Burned, warped or pitted valves.

6. Replace as necessary.

7. Plugged or restricted exhaust
system.

7. Inspect and replace as
necessary.

8. Faulty coil.

8. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

ENGINE MISSES ON
ACCELERATION

1. Spark plugs dirty or incorrectly
gapped.

1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).

2. Dirt in fuel system.

2. Clean fuel system.

3. Burned, warped or pitted valves.

3. Replcae as necessary.

4. Faulty coil.

4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

ENGINE MISSES AT HIGH SPEED

1. Spark plugs dirty or incorrectly
gapped.

1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).

2. Faulty coil.

2. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).

3. Dirt or water in fuel system.

3. Clean system and replace fuel
filter.

ENGINE - 4.7L SERVICE INFORMATION

9 - 1193

DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - MECHANICAL

CONDITION

POSSIBLE CAUSES

CORRECTIONS

NOISY VALVES

1. High or low oil level in
crankcase.

1. (Refer to LUBRICATION &
MAINTENANCE -
SPECIFICATIONS)

2. Thin or diluted oil.

2. Change oil and filter.

3. Low oil pressure.

3. Check oil pump, if Ok, check rod
and main bearings for excessive
wear.

4. Dirt in lash adjusters.

4. Replace as necessary.

5. Worn rocker arms.

5. Replace as necessary.

6. Worn lash adjusters

6. Replace as necessary.

7. Worn valve guides.

7. (Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES
& SEATS - STANDARD
PROCEDURE)

8. Excessive runout of valve seats
on valve faces.

8. (Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES
& SEATS - STANDARD
PROCEDURE)

CONNECTING ROD NOISE

1. Insufficient oil supply.

1. (Refer to LUBRICATION &
MAINTENANCE -
SPECIFICATIONS)

2. Low oil pressure.

2. Check oil pump, if Ok, check rod
and main bearings for excessive
wear.

3. Thin or diluted oil.

3. Change oil and filter.

4. Excessive bearing clearance.

4. Replace as necessary.

5. Connecting rod journal
out-of-round.

5. Service or replace crankshaft.

6. Misaligned connecting rods.

6. Replace bent connecting rods.

MAIN BEARING NOISE

1. Insufficient oil supply.

1. (Refer to LUBRICATION &
MAINTENANCE -
SPECIFICATIONS)

2. Low oil pressure.

2. Check oil pump, if Ok, check rod
and main bearings for excessive
wear.

3. Thin or diluted oil.

3. Change oil and filter.

4. Excessive bearing clearance.

4. Replace as necessary.

5. Excessive end play.

5. Check thrust washers for wear.

6. Crankshaft journal out-of round.

6. Service or replace crankshaft.

7. Loose flywheel or torque
converter.

7. Tighten to correct torque

9 - 1194

ENGINE - 4.7L SERVICE INFORMATION

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