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 DIAGNOSTIC PROCEDURES article and SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article were performed before diagnosing a symptom. Symptom checks are listed in order of probability, ease of accomplishment, and accessibility. Symptoms available for diagnosis are as follows:

• ROUGH OR ROLLING IDLE, STALLS, MISSES, HESITATION OR SURGE 
• HARD START/LONG CRANK OR ERRATIC START/CRANK 
• NO START/NORMAL CRANK 
• SLOW RETURN TO IDLE 
• FAST IDLE (DIESELS/RUNS ON) 
• LOW IDLE (STALLS ON DECELERATION) 
• BACKFIRES 
• LACK/LOSS OF POWER 
• SPARK KNOCK 
• POOR FUEL ECONOMY 
• EMISSIONS COMPLIANCE 
• HISSING SOUND WHEN REMOVING FUEL CAP 
• EXCESSIVE FUEL ODOR 
• UNABLE TO REFUEL VEHICLE 
• WARNING INDICATOR LIGHTS 
• AUTOMATIC TRANSMISSION DOWN OR UPSHIFT, OR ENGAGEMENT 
• SPEEDOMETER OR TACHOMETER INOPERATIVE 
• HIGH OIL CONSUMPTION 
• ELECTRIC COOLING FAN INOPERATIVE AT LOW, MEDIUM &/OR HIGH SPEED, OR HYDRAULIC COOLING FAN INOPERATIVE (LS) 
• ELECTRIC OR HYDRAULIC COOLING FAN(S) ALWAYS ON 
• EXHAUST SMOKE 
• FUEL ODOR 
• ENGINE NOISE 
• CLIMATE CONTROL (LACK OF COOLING OR A/C INOPERATIVE) 
• CLIMATE CONTROL (A/C ALWAYS ON) 
• A/C DOES NOT TURN OFF DURING WOT 
• EXHAUST ODOR (SULFUR SMELL)