Oil Burning: If your Nissan Stanza is burning excessive oil, it can cause grayish-black smoke to come out of the exhaust pipe. This can happen due to worn-out piston rings, valve stem seals, or other engine components that let oil seep into the combustion chamber.
Rich Fuel Mixture: A fuel mixture that's too rich (too much fuel compared to air) can also create grayish-black smoke. This can be caused by a malfunctioning fuel injector, a faulty oxygen sensor, or other issues that affect fuel delivery or air-fuel ratio.
Coolant Leakage: If there's a coolant leak, especially from a blown head gasket or cracked engine block, it can enter the combustion chamber and produce grayish-black smoke along with a sweet smell.
Turbocharger Issues: If your Nissan Stanza has a turbocharger, problems like damaged seals or a faulty wastegate can cause oil to leak and burn, resulting in grayish-black smoke.
EGR (Exhaust Gas Recirculation) System: A faulty EGR valve or problems with the EGR system can lead to grayish-black smoke as unburnt fuel and exhaust gases mix in the engine.
Catalytic Converter Problems: In some cases, grayish-black smoke can indicate issues with the catalytic converter, which helps clean exhaust emissions. A clogged or damaged catalytic converter can cause incomplete combustion and produce excessive smoke.
Poor Engine Maintenance: Lack of regular maintenance, such as neglecting oil changes or ignoring other routine servicing, can contribute to the buildup of deposits in the engine, leading to grayish-black smoke.
Fuel Quality: Using low-quality or contaminated fuel can cause incomplete combustion and produce grayish-black smoke.
