INTRODUCTION
Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING and TESTS W/CODES (if applicable) articles. Use this article to diagnose driveability problems existing when a hard fault code is not present or vehicle is not equipped with a self-diagnostic system.
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 are intended to direct the technician to malfunctioning component(s) so further diagnosis may be performed. A symptom should lead to specific component or system testing, or an adjustment specification.
Use intermittent test procedures to locate driveability problems that DO NOT occur when the vehicle is being tested. 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 SYSTEM/COMPONENT TESTS article. For specifications, see ADJUSTMENTS or SPECIFICATIONS articles.
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 BASIC TESTING and TESTS W/CODES articles have been performed before attempting to diagnose a symptom. Symptoms available for diagnosis include the following. Recommended system and component checks may not apply to all vehicles.
- Engine won't start
- Difficult cold start
- Fast idle out of specification
- Rough idle when warm
- Idle RPM high when warm
- Idle RPM low when warm
- Stalling during warm up
- Stalling after warm up
- Misfire or rough operation
- Emission test failure
- Lack of power
ACCORD, CIVIC & CRX
Check spark and fuel systems as outlined in BASIC TESTING and SYSTEM/COMPONENT TESTS . Test ECU power and ground circuits. On Accord, check TDC/Crank/Cyl sensor and ignition output circuits also.
PRELUDE
Check fuel system and spark.
ACCORD
Check coolant temperature, MAP, atmospheric pressure and TDC/CRANK/CYL sensor circuits for malfunctions. Check fast idle and air boost valves for proper operation.
CIVIC 1.5L & CRX (STD.)
Check MAP, coolant temperature and Electronic Air Control Valve (EACV).
CIVIC 1.6L & CRX (HF & SI)
Check fuel injectors and circuits also.
Check coolant temperature and carburetor for malfunctions.
Check Electric Air Control Valve (EACV), fast idle and air boost valves for proper operation. Check coolant temperature sensor circuit for shorts, power and ground.
Check coolant temperature sensor and carburetor choke circuit.
Check Electric Air Control Valve (EACV), MAP sensor and fuel injectors for proper operation.
Verify proper operation of MAP and intake air temperature sensors. Check carburetor idle circuit.
Check Electric Air Control Valve (EACV), fast idle and air boost valves for proper operation.
CIVIC & CRX
Check Electric Air Control Valve (EACV), fast idle and air boost valves for proper operation. Check coolant temperature sensor circuit. On Civic 1.5L, verify proper electric load detector operation.
Check automatic transmission shift position signal, A/C signal circuits and carburetor.
Check Electric Air Control Valve (EACV), fuel injector circuit and electric load detector.
Verify proper EACV operation and carburetor.
Check Electric Air Control Valve (EACV), fast idle valve, air boost valve and fuel system. Check coolant temperature sensor operation.
Check MAP sensor, ignition output signal and EACV.
Check EACV, fast idle valve, air boost valve and fuel system.
Verify proper MAP sensor operation, coolant temperature sensor and carburetor.
Check fuel system, air boost valve, Electric Air Control Valve (EACV) and EGR control system. Check atmospheric pressure sensor.
CIVIC 1.5L & CRX (HR & SI)
Check fuel system, air boost valve, EACV and EGR control system.
CIVIC 1.6L
Check EACV, air boost valve and fuel system.
CRX (STD.)
Check EACV, fuel system and EGR control system.
Verify proper MAP sensor and carburetor operation.
Check Electric Air Control Valve (EACV), fuel injectors and EGR control system. Check TDC/CRANK/CYL sensor for circuit integrity.
Check fuel system, EGR control system and EACV.
Check EACV and fuel injectors.
Check proper operation of oxygen sensor, vehicle speed pulser, MAP sensor, carburetor and fuel system.
Check MAP sensor and oxygen sensor. Check emission control and fuel systems.
Check MAP sensor and oxygen sensor.
Check MAP sensor, oxygen sensor, carburetor, air intake system, Electric Air Control Valve (EACV) and all other emission control systems.
LACK OF POWER
Check MAP sensor (if equipped), throttle angle sensor, fuel injectors (if equipped), air intake system and all emission control systems.
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 (on some systems) 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 is in ON position, or engine is running. Ensure ignition 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
- Lightly vibrate component.
- Heat component.
- Wiggle or bend wiring harness.
- Spray component with water.
- 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.
See also:
• ADJUSTMENTS
• SPECIFICATIONS