Engine Controls - Tests W/o Codes - Sbec Dodge Shadow I

INTRODUCTION

Before attempting to diagnose symptoms or intermittent faults, ensure steps in BASIC DIAGNOSTIC PROCEDURES and SELF-DIAGNOSTICS (if applicable) articles have been performed. Use this article to diagnose driveability problems that exist when a hard fault code is not present.

Symptom checks are intended to direct the technician to malfunctioning component(s) so further diagnosis may be performed. A symptom should lead to further testing of specific components or systems, or verification of adjustment specifications.

Use intermittent test procedures to locate intermittent driveability problems that do not occur when the vehicle is being tested. These problems may cause a noticeable driveability problem or cause the malfunction warning light to illuminate on some vehicles.

It is also possible that certain driveability concerns have been rectified by the manufacturer through substitution of a revised calibration chip or computer control unit. Check with manufacturer for latest information on updated chips and control units.

Note. For specific testing procedures, refer to appropriate I - SYSTEMS & COMPONENT TESTS article. For verifying specifications, refer to appropriate ADJUSTMENTS article.

SYMPTOM DIAGNOSIS

Symptom checks cannot be used properly unless the problem is actually happening while vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC TESTING and G - TESTING W/CODES (if applicable) articles have been performed before attempting to diagnose a symptom. Symptoms available for diagnosis include

1. No Start - Cold Engine
2. No Start - Warm Engine
3. Starts But Stalls
4. Hard To Start - Cold Engine
5. Erratic Idle - Warm-Up
6. Backfiring
7. Incorrect Idle Speed
8. Hesitation - Acceleration
9. Hesitation - Coasting
10. Knocking
11. Engine Misfire - All Conditions
12. Insufficient Engine Power
13. Poor Fuel Economy
14. Excessive HC and NOx

NO START - COLD ENGINE

1. Ensure battery is fully charged
2. Check spark plugs
3. Check fuel pump fuse(s)
4. Check in-line fuse to control unit (if applicable)
5. Ensure ignition timing and fuel pressure are correct
6. Check fuel injectors
7. Ensure timing belt is not broken (if applicable)
8. Ensure ignition coil resistance is correct
9. Ensure rotor, distributor and plug wires are okay
10. Check ignition control unit
11. Check coolant temperature sensor and connector
12. Check throttle switch and connector (if applicable)
13. Check engine speed sensor
14. Check airflow sensor

NO START - WARM ENGINE

1. Ensure fuel pressure is correct
2. Check for gasoline in oil
3. Ensure fuel injectors are not leaking
4. Check ignition and sensor wires for proper connection
5. Ensure spark plugs are not fouled
6. Check ignition and coil circuit
7. Check engine speed sensor
8. Check throttle switch and connector (if applicable)

STARTS BUT STALLS

1. Check coolant temperature sensor
2. Check ignition and sensor wires for proper connection
3. Check fuel injectors
4. Check throttle switch and connector (if applicable)
5. Check engine speed sensor

HARD TO START - COLD ENGINE

1. Check spark plugs
2. Check distributor (if applicable)
3. Ensure fuel pressure is correct
4. Check ignition timing
5. Check throttle switch and connector (if applicable)

ERRATIC IDLE - WARM-UP

1. Check throttle switch and connection (if applicable)
2. Check coolant temperature sensor and connection
3. Check air temperature sensor (if applicable)
4. Ensure spark plugs are not fouled
5. Check ignition and sensor wires for proper connection
6. Check distributor (if applicable)
7. Check ignition and coil circuit
8. Check intake system
9. Check engine speed sensor
10. Check throttle switch and connector (if applicable)
11. Check MAP sensor (if applicable)

BACKFIRING

1. Ensure ignition timing is correct
2. Ensure timing belt has not jumped
3. Check distributor (if applicable)
4. Check for gasoline in oil
5. Ensure fuel injectors are not leaking
6. Check spark plugs
7. Check ignition and coil circuit
8. Check engine speed sensor
9. Check throttle switch and connector
10. Check exhaust system

INCORRECT IDLE SPEED

1. Check fuel injectors
2. Check intake system for leaks
3. Check coolant temperature sensor
4. Check throttle switch and connector (if applicable)
5. Check distributor (if applicable)

HESITATION - ACCELERATION

1. Check ignition and sensor wires for proper connection (if applicable)
2. Ensure spark plug wires are okay
3. Ensure spark plugs are not fouled
4. Check MAP sensor (if applicable)
5. Check throttle switch and connector (if applicable)
6. Check ignition and coil circuit
7. Check engine speed sensor

HESITATION - COASTING

1. Check fuel injectors
2. Check ignition and sensor wires for proper connection
3. Check throttle switch and connector
4. Check engine speed sensor
5. Check for gasoline in oil

KNOCKING

1. Check ignition and coil circuit
2. Ensure spark plugs fire
3. Check knock sensor (if applicable)
4. Check throttle switch and connector (if applicable)
5. Check engine speed sensor
6. Check MAP sensor (if applicable)

ENGINE MISFIRE - ALL CONDITIONS

1. Check fuel injectors
2. Check ignition and sensor wires for proper connection
3. Check ignition and coil circuit
4. Check for gasoline in oil
5. Check intake and exhaust system
6. Check throttle switch and connector (if applicable)
7. Check for vacuum leaks
8. Check engine speed sensor
9. Check MAP sensor (if applicable)

INSUFFICIENT ENGINE POWER

1. Check fuel injectors
2. Ensure fuel pressure is correct
3. Check airflow sensor
4. Check for restricted exhaust
5. Check coolant temperature sensor
6. Check air temperature sensor (if applicable)
7. Check throttle switch and connector (if applicable)
8. Check ignition and coil circuit
9. Check MAP sensor (if applicable)
10. Check engine speed sensor
11. Check intake and exhaust system

POOR FUEL ECONOMY

1. Check for leaky fuel injectors
2. Ensure spark plugs are not fouled
3. Check for faulty oxygen sensor
4. Check throttle switch and connector
5. Check for poor wire connections and fouled spark plugs
6. Check engine speed sensor
7. Check for gasoline in oil
8. Check MAP sensor (if applicable)

EXCESSIVE HC AND NOx

1. Check for gasoline in oil
2. Check for leaky fuel injectors
3. Check for faulty oxygen sensor
4. Check ignition and sensor wires for poor connection
5. Check engine speed sensor
6. Check throttle switch and connector (if applicable)
7. Check for vacuum leaks

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires the duplication of circuit or component failure in order to identify the fault. These procedures may lead to the computer recording a fault code (on some systems) which may help in diagnosis.

If problem vehicle does not produce fault codes, it will be necessary to monitor voltage or resistance values using a digital volt-ohmmeter (DVOM) while attempting to reproduce conditions which will create an intermittent fault. A change in status on the DVOM will indicate a fault has been located.

When using a voltmeter to pinpoint faults, monitor voltage reading with ignition on, or vehicle running. A change in status on the voltmeter while performing intermittent test procedures will indicate area of fault.

When using an ohmmeter to detect problems in the circuit, monitor circuit resistance (ohms) with ignition switch in the OFF position, or with battery disconnected. A change in ohmmeter reading while performing test procedures will indicate area of fault.

INTERMITTENT SIMULATION

To reproduce the conditions which create an intermittent fault so that it may be identified during testing, some of the following methods may be used

1. Applying light vibration to components.
2. Heating a component.
3. Wiggling or bending a wiring harness.
4. Applying humidity to a component.
5. Removing or applying a vacuum supply source.

Monitor circuit/component voltage or resistance while attempting to simulate intermittent. If vehicle is running, monitor for self-diagnostic codes. Use the results of these tests to identify a faulty component or an area which should be checked closely for the problem.