INTRODUCTION
Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING and TESTS W/CODES articles in this 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 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 adjustment specification.
Use intermittent test procedures to locate driveability problems which 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 in this section. For specifications, see SPECIFICATIONS or ADJUSTMENTS article in this section.
SYMPTOM DIAGNOSIS
Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC TESTING and TESTS W/CODES articles in this section were performed before attempting to diagnose a symptom. Symptoms available for diagnosis include these symptoms.
- Engine will not 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 Recommended system and component checks may not apply to all vehicles.
ENGINE WILL NOT START
Check spark and fuel systems as outlined in BASIC TESTING and SYSTEM/COMPONENT TESTS articles in this section. Test ECU power and ground circuits. On Accord and Prelude, check TDC/CRANK/CYL sensor and ignition output circuits.
Accord
Check coolant temperature, MAP, atmospheric pressure and TDC/CRANK/CYL sensor circuits for malfunctions. Also check fast idle and air boost valves for proper operation.
Civic & CRX 1.5L (TBI)
Check MAP and coolant temperature sensors and Electronic Air Control Valve (EACV).
Civic & CRX 1.5L & 1.6L (PFI)
Check fuel injectors and MAP and coolant temperature sensors.
Prelude
Check coolant temperature, TDC/CRANK/CYL, atmospheric pressure and MAP sensors.
Accord, Civic & CRX
Check Electric Air Control Valve (EACV) and fast idle and air boost valves for proper operation. Also check coolant temperature sensor circuit for short circuit to power or ground.
Check Electronic Air Control Valve (EACV), fast idle valve, idle adjusting screw and coolant temperature sensor.
ROUGH IDLE WHEN WARM
Check Electric Air Control Valve (EACV), MAP sensor, fuel injectors and EGR system for proper operation.
Check Electric Air Control Valve (EACV) and fast idle and air boost valves for proper operation.
Civic & CRX
Check Electric Air Control Valve (EACV), electric load detector and fast idle and air boost valves for proper operation. Also check coolant temperature sensor circuit.
Check Electronic Air Control Valve (EACV), fast idle valve, oil pressure switch signal, vacuum hose connections and A/C signal circuit.
Check Electric Air Control Valve (EACV), fuel injector circuit, A/C signal circuit and electric load detector.
Check Electronic Air Control Valve (EACV), fuel injectors, oil pressure switch and A/T position signal and A/C signal circuits.
Check Electric Air Control Valve (EACV), fast idle valve, air boost valve and fuel system. Also check coolant temperature sensor.
Check Electronic Air Control Valve (EACV), ignition output signal and MAP sensor.
Check Electronic Air Control Valve (EACV), fast idle valve, air boost valve and fuel system.
Check Electronic Air Control Valve (EACV), fuel system and coolant temperature sensor operation.
Check fuel system, air boost valve, Electric Air Control Valve (EACV) and EGR control system. Also check atmospheric pressure sensor.
Check Electronic Air Control Valve (EACV), fuel system and EGR system.
Check Electronic Air Control Valve (EACV), air boost valve, fuel system and EGR system.
Check idle adjustments, fuel system, Electronic Air Control Valve (EACV), EGR system and atmospheric pressure sensor.
Accord & Prelude
Check fuel injectors, Electric Air Control Valve (EACV) and EGR system. Also check TDC/CRANK/CYL sensor for circuit integrity.
Check fuel system, EGR system and Electronic Air Control Valve (EACV).
Check fuel injectors, Electronic Air Control Valve (EACV) and EGR system.
Check MAP sensor and oxygen sensor. Also check emission control and fuel systems.
Check fuel system, MAP sensor and oxygen sensor.
Check fuel injectors, MAP sensor and oxygen sensor.
Check fuel injectors, MAP sensor, oxygen sensor, Electric Air Control Valve (EACV) and all other emission control systems.
LACK OF POWER
Check MAP sensor, throttle angle sensor, fuel injectors, air intake system and all emission control systems.
INTERMITTENT PROBLEM DIAGNOSIS
Intermittent fault testing requires duplicating circuit or component failure to identify problem. These procedures may lead to 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 on or engine is running. Ensure ignition is off or negative battery cable is disconnected when monitoring circuit resistance. Status changes on DVOM during test procedures indicate area of fault.
TEST PROCEDURES
Intermittent Simulation
To reproduce conditions creating an intermittent fault, use 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:
• SPECIFICATIONS
• ADJUSTMENTS