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 in the ENGINE PERFORMANCE Section were performed before diagnosing a symptom. Symptoms available for diagnosis include:

• Difficult or no start (cranks okay)
• Engine misfires or has lack of power
• Rough or unstable idle
• Engine hesitates
• Engine surges
• Spark knock/detonation
• Poor fuel mileage
• Fails emission test