SYMPTOM DIAGNOSIS
Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in appropriate BASIC TESTING article and appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section were performed before diagnosing a symptom. See BASIC TESTING and TESTS W/CODES TABLE in this article. Following symptoms are available for diagnosis.
- Difficult To Start Or Will Not Start
- Rough Or Unstable Idle
- High Idle After Warm Up
- Engine Stalls
- Engine Misfires Or Has Lack Of Power
- Engine Runs Rough On Deceleration
- Backfire In Exhaust System
- Poor Fuel Mileage
- Excessive Oil Consumption
- Abnormal Noise Or Knocking
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 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.