* Blue/Grey Smoke: This usually points to burning oil. Possible causes include:
* Worn piston rings: Allow oil to seep into the combustion chamber.
* Worn valve seals: Oil leaks past the valve stems.
* Bad PCV valve: A faulty positive crankcase ventilation valve allows excessive oil vapor into the intake.
* Leaking valve cover gasket: Oil leaks onto hot engine parts and burns.
* White Smoke: This often suggests burning coolant. Possible causes include:
* Blown head gasket: A crack in the head gasket allows coolant to mix with combustion gases.
* Cracked cylinder head: A crack in the cylinder head can also allow coolant to enter the combustion chamber.
* Faulty cylinder head: A warped or damaged cylinder head can cause similar problems.
* Black Smoke: This usually means the engine is running rich (too much fuel). Possible causes include:
* Faulty fuel injectors: Injecting too much fuel into the cylinders.
* Mass airflow sensor (MAF) problem: An inaccurate MAF sensor reading leads to incorrect fuel delivery.
* Dirty air filter: Restricts airflow, causing a rich mixture.
* Throttle position sensor (TPS) issue: Incorrect throttle position readings leading to over-fueling.
Other Considerations:
* Amount of smoke: A small amount of smoke on startup, especially in cold weather, might be condensation and not a serious issue. However, excessive smoke at any time is a problem.
* When the smoke appears: Smoke only on startup might indicate different issues than constant smoke while driving.
* Engine performance: Is the engine running rough, losing power, or overheating? This information helps pinpoint the problem.
What to do:
Do *not* continue driving with excessive smoke. This could cause significant engine damage. Have your Mercury Mountaineer inspected by a qualified mechanic as soon as possible. They can properly diagnose the cause of the smoke and recommend the necessary repairs. Providing them with details about the color, amount, and circumstances of the smoke will help them in their diagnosis.
