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 below were performed before diagnosing a symptom.
- «BASIC TESTING»(ref-23408)
- «TESTS W/CODES»(ref-23407)
Symptoms available for diagnosis include
- Backfire Through Induction Or Exhaust
- Dieseling (Run-On)
- Lack Of Power
- Spark Knock (Pinging)
- Stalls/Quits
- Stumble/Hesitation During Acceleration
- Misses/Surges
- Idle Is Fast/Slow Return To Idle
- Idle Is Rough
- Engine Speeds Up
- Cranks Normally/No Start
- Cranks Normally/Slow To Start
- Poor Fuel Economy
- Exhaust Smoke/Odor
- Fuel Odor/Leaks
- Fails Emission Test
FAILS EMISSION TEST
- Check canister purge control solenoid.
- Check pressure regulator control solenoid.
- Check exhaust gas oxygen sensor.
- Check by-pass air control valve.
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 with 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.
See also:
• SYSTEM/COMPONENT TESTS