POTENTIAL CAUSE
1. Low quality fuel.
2. Injection pump/engine timing is retarded.
3. Engine coolant entering combustion chamber through blown gasket, cracked head, loose/damaged head bolts. May be accompanied by low coolant level and overheating.
4. Low ambient temperatures (below freezing).
CORRECTION
1. Drain and refill tank with better quality fuel.
2. Check and correct timing.
3. Verify problem and repair as necessary. Replace cracked head, block, or head gasket.
4. Normal condition caused primarily by water vapor. Not a concern unless it continues after warmup.
