Engine Controls - Tests W/o Codes Plymouth Acclaim I

INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform steps in appropriate BASIC TESTING and G - TESTS W/ CODES articles in the ENGINE PERFORMANCE Section. Use this article to diagnose driveability problems existing when a hard fault code is not present.

Note. Some driveability problems may have been corrected by manufacturer with a revised computer calibration chip or computer control unit. Check with manufacturer for latest chip or computer application.

Symptom checks direct the technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component, system test or adjustment.

Use intermittent test procedures to locate driveability problems that do not occur when the vehicle is being tested. These problems may cause a noticeable driveability problem or cause the check engine light to illuminate on some vehicles. These test procedures should also be used if a soft (intermittent) trouble code was present, but no problem was found during self-diagnostic testing.

Note. For specific testing procedures, see I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. For specifications, see appropriate ADJUSTMENTS or SPECIFICATIONS article in the ENGINE PERFORMANCE Section.

SYMPTOM DIAGNOSIS

Symptom checks cannot be used properly unless the problem occurs while the vehicle is being tested. To reduce diagnostic time, ensure steps in appropriate BASIC DIAGNOSTIC PROCEDURES and SELF-DIAGNOSTICS articles were performed before diagnosing a symptom. These symptoms are available for diagnosis.

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 & NOx

NO START - COLD ENGINE

1. Ensure battery is fully charged.
2. Check spark plugs.
3. Check fuel pump fuse(s).
4. Ensure ignition timing and fuel pressure are correct.
5. Check fuel injectors.
6. Check crank and cam sensors (DIS system).
7. Ensure timing belt/chain has not jumped.
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 position sensor and connector.
13. Check airflow sensor.
14. Check anti-theft system (if applicable).

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 crank and cam sensors (DIS system).
8. Check throttle position sensor and connector.

STARTS BUT STALLS

1. Check coolant temperature sensor.
2. Check ignition and sensor wires for proper connection.
3. Check fuel injectors.
4. Check throttle position sensor and connector.
5. Check anti-theft system (if applicable).
6. Check crank and cam sensor (DIS system).

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 position sensor and connector.

ERRATIC IDLE - WARM-UP

1. Check throttle position sensor and connector.
2. Check coolant temperature sensor and connector.
3. Check air temperature sensor (turbo only).
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 crank and cam sensors (DIS system).
10. Check MAP sensor.
11. Check for contaminated fuel.

BACKFIRING

1. Ensure ignition timing is correct.
2. Ensure timing belt/chain 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 and plug wires.
7. Check distributor cap and rotor (if applicable).
8. Check ignition and coil circuit.
9. Check crank and cam sensors (DIS system).
10. Check throttle switch and connector.
11. Check exhaust system.

INCORRECT IDLE SPEED

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

HESITATION - ACCELERATION

1. Check ignition and sensor wires for proper connection.
2. Check distributor cap for moisture (if applicable).
3. Check distributor cap for carbon tracking (if applicable).
4. Ensure spark plug wires are okay.
5. Ensure spark plugs are not fouled.
6. Check EGR valve operation.
7. Check MAP sensor.
8. Check throttle position sensor and connector.
9. Check ignition and coil circuit.
10. Check crank and cam sensors (DIS system).

HESITATION - COASTING

1. Check fuel injectors.
2. Check ignition and sensor wires for proper connection.
3. Check throttle switch and connector.
4. Check crank and cam sensors (DIS system).
5. Check for gasoline in oil.

KNOCKING

1. Check ignition timing.
2. Check EGR valve operation.
3. Check ignition and coil circuit.
4. Ensure spark plugs fire.
5. Check knock sensor (if applicable).
6. Check throttle position sensor and connector.
7. Check engine speed sensor.
8. Check MAP sensor.

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 position sensor and connector.
7. Check for vacuum leaks.
8. Check EGR valve operation.
9. Check engine speed sensor.
10. Check MAP sensor.

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 (turbo only).
7. Check throttle position sensor and connector.
8. Check ignition and coil circuit.
9. Check MAP sensor.
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 contaminated fuel.
8. Check for gasoline in oil.
9. Check MAP sensor.

EXCESSIVE HC & 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 EGR valve operation.
6. Check crank and cam sensors (DIS system).
7. Check throttle position sensor and connector.
8. Check for vacuum leaks.

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to the computer setting a fault code which may help in diagnosis.

If problem vehicle does not produce fault codes, monitor voltage or resistance values using a DVOM while attempting to reproduce conditions causing intermittent fault. A status change on DVOM indicates a fault has been located.

Use a DVOM to pinpoint faults. When monitoring voltage, ensure ignition switch is in ON position or engine is running. Ensure ignition switch is in OFF position or negative battery cable is disconnected when monitoring circuit resistance. Status changes on DVOM during test procedures indicate area of fault.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods

1. Lightly vibrate component.
2. Heat component.
3. Wiggle or bend wiring harness.
4. Spray component with water.
5. Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.