engine is a double overhead camshaft design with
hydraulic lifters and four valves per cylinder (Fig. 1).
The engine does not have provisions for a free wheel-
ing valve train.

The cylinders are numbered from front to rear,

with the right bank odd numbered, and the left bank
even numbered (Fig. 2). The firing order is 1–2–3–4–
5–6.

The engine identification number is located on the

rear of the cylinder block just below the left cylinder
head (Fig. 3)

Fig. 1 2.7 Liter Engine

Fig. 2 Cylinder Numbering and Firing Order

Fig. 3 Engine Identification

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ENGINE 2.7L DOHC

DIAGNOSIS AND TESTING

DIAGNOSIS AND TESTING - ENGINE
DIAGNOSIS - INTRODUCTION

Engine diagnosis is helpful in determining the

causes of malfunctions not detected and remedied by
routine maintenance.

These malfunctions may be classified as either

mechanical (e.g., a strange noise), or performance
(e.g., engine idles rough and stalls).

Refer to Service Diagnosis—Mechanical Chart and

Service Diagnosis—Performance Chart, for possible
causes and corrections of malfunctions. Refer to
FUEL SYSTEM for the fuel system diagnosis.

Additional tests and diagnostic procedures may be

necessary for specific engine malfunctions that can-
not be isolated with the Service Diagnosis charts.
Information concerning additional tests and diagno-
sis is provided within the following:

• Cylinder Compression Pressure Test

• Cylinder Combustion Pressure Leakage Test

• Cylinder Head Gasket Failure Diagnosis

• Intake Manifold Leakage Diagnosis

• Lash Adjuster (Tappet) Noise Diagnosis

• Engine Oil Leak Inspection

DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - PERFORMANCE

CONDITION

POSSIBLE CAUSE

CORRECTION

ENGINE WILL NOT START

1. Weak battery.

1. Test battery. Charge or replace
as necessary. (Refer to 8 -
ELECTRICAL/BATTERY SYSTEM/
BATTERY - DESCRIPTION)

2. Corroded or loose battery
connections.

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

3. Faulty starter.

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

4. Faulty coil(s) or control unit.

4. Test and replace as needed.
(Refer to Appropriate Diagnostic
Information)

5. Incorrect spark plug gap.

5. Check and adjust gap as needed.

6. Contamination in fuel system.

6. Clean system and replace fuel
filter.

7. Faulty fuel pump.

7. Test fuel pump and replace as
needed. (Refer to Appropriate
Diagnostic Information)

8. Incorrect engine timing.

8. Check for a skipped timing chain.

ENGINE STALLS OR IDLES
ROUGH

1. Idle speed too low.

1. Test minimum air flow. (Refer to
Appropriate Diagnostic Information)

2. Incorrect fuel mixture.

2. (Refer to Appropriate Diagnostic
Information)

3. Intake manifold leakage.

3. Inspect intake manifold gasket,
manifold, and vacuum hoses.

4. Faulty coil(s).

4. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)

ENGINE 2.7L DOHC

9 - 153

ENGINE 2.7L DOHC (Continued)

CONDITION

POSSIBLE CAUSE

CORRECTION

ENGINE LOSS OF POWER

1. Dirty or incorrectly gapped plugs.

1. Set gap as needed or replace
plug(s).

2. Contamination in fuel system.

2. Clean system and replace fuel
filter.

3. Faulty fuel pump.

3. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)

4. Incorrect valve timing.

4. Correct valve timing as needed.

5. Leaking cylinder head gasket.

5. Replace cylinder head gasket.

6. Low compression.

6. Test compression of each
cylinder.

7. Burned, warped, or pitted valves.

7. Replace valves.

8. Plugged or restricted exhaust
system.

8. Check exhaust system restriction.
Replace parts, as necessary.

9. Faulty coil(s).

9. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)

ENGINE MISSES ON
ACCELERATION

1. Dirty or incorrectly gapped spark
plugs.

1. Set gap as needed or replace
plug(s).

2. Contamination in Fuel System.

2. Clean fuel system and replace
fuel filter.

3. Burned, warped, or pitted valves.

3. Replace valves.

4. Faulty coil(s).

4. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)

ENGINE MISSES AT HIGH SPEED

1. Dirty or incorrect spark plug gap.

1. Set gap as needed or replace
plug(s).

2. Faulty coil(s).

2. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)

3. Dirty fuel injector(s).

Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)

4. Contamination in fuel system.

4. Clean system and replace fuel
filter.

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ENGINE 2.7L DOHC

ENGINE 2.7L DOHC (Continued)

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