Engine Smoke Diagnosis
Stop Driving
Smoke from the engine bay or exhaust tailpipe means something is burning that should not be. The color, location, and smell each narrow the cause. White or gray steam from under the hood usually means a coolant or overheating problem. Blue-gray smoke from the tailpipe points to oil burning. Black exhaust smoke points to a rich fuel condition. Smoke under the hood with an acrid smell may indicate an electrical short.
Stop driving — this can cause serious damage or be unsafe.
Check These First
Before diving into diagnosis, quickly verify these:
- 1Note the smoke color: white or light gray steam, blue or gray haze, or black smoke from the tailpipe.
- 2Note where the smoke is coming from — the tailpipe only, from under the hood, or both.
- 3Check whether the temperature gauge is rising above normal.
- 4Check for a sweet smell (coolant), an oil smell (burning oil), or an acrid plastic smell (electrical short).
- 5Pull over immediately if smoke is heavy, the temperature gauge is rising, or the smell is electrical.
Most Likely Causes
Ranked from most to least common — start at the top.