CONTENTS
SOUNDS
UNDERHOOD
RHYTHMIC

ENGINE KNOCKS OR PINGS

CONDITION(S)

• ENGINE KNOCKS OR PINGS WHEN ACCELERATING
• SOUNDS LIKE A LITTLE HAMMER HITTING THE SIDE OF THE ENGINE (DETONATION)
• MILD PING (PREIGNITION) NORMAL ON SOME MODERN CARS
• ENGINE IS A DIESEL AND ABNORMALLY LOUD KNOCKING SOUND OCCURS

POTENTIAL CAUSE(S)

CHECK THESE FIRST:

1. GASOLINE TOO LOW IN OCTANE
Use gasoline of higher octane rating.

2. ENGINE OVERHEATING (PREIGNITION)
Have cause of overheating professionally corrected.

3. ADVANCED IGNITION TIMING
Have ignition timing professionally retarded.

CHECK THESE NEXT:

4. FAULTY OR DISCONNECTED EXHAUST GAS RECIRCULATION (EGR) VALVE STUCK CLOSED
Connect EGR vacuum hose or have EGR valve professionally serviced.

5. EXTREMELY LEAN FUEL/AIR MIXTURE
Have fuel/air mixture professionally adjusted (enriched).

6. SPARK PLUG HEAT RANGE TOO HIGH
Install new spark plug(s) with lower heat range.

CHECK THESE LAST:

7. FAULTY DISTRIBUTOR ADVANCE
Have distributor advance professionally repaired.

8. EXHAUST MANIFOLD HEAT CONTROL VALVE (HEAT RISER) STUCK CLOSED
Have heat riser professionally repaired.

CONTENTS
MUFFLED, BELL-LIKE SOUND
LIGHT, TAPPING NOISE