Smoking Vehicles

Do Your Share For Cleaner Air

Tips on how to prevent and control the problem. From the Texas Natural Resource Conservation Commission.

See a Smoking Vehicle? Call 1-800-453-SMOG

What causes excess smoke from motor vehicle tailpipes and why is it a problem?

Tailpipe smoke is caused by incomplete fuel combustion. This usually results from improper engine operation in both gasoline and diesel powered vehicles. Visible exhaust smoke can vary in color and composition depending on the type of problem. Lack of proper maintenance of you motor vehicle's engine may increase exhaust smoke. Tailpipe smoke lasting 10 seconds or longer indicates problems not only for your motor vehicle but also for the air that we breathe. If the exhaust smoke from ANY light-duty gasoline or diesel powered vehicle is visible for more than 10 consecutive seconds, it is in violation of Texas regulations established to safeguard air quality.

White or Cold Smoke comes from a cold-running engine and is caused by unburned fuel. It is usually associated with start-up for both gasoline and diesel engines and should disappear or change colors as the engine warms up. Not a problem if it clears.

Black/Gray or Dirty Smoke is the most common type of smoke and is a result of unburned carbon particles (soot). This smoke is associated with incomplete fuel combustion in both gasoline and diesel, as a result of excessive fuel supply or not enough air. The smoke problem is associated with the fuel injection system, air intake system, or exhaust system. Some of the repairs that will correct this problem are simple and can be performed at small expense. In most cases, these repairs will pay for themselves by reducing vehicle operating costs. Maintenance may include: cleaning or replacing fuel injectors, air filters, spark plugs or changing the oil and oil filter.

Blue Smoke is a result of burning engine oil that has leaked into the combustion chamber. Excessively worn piston rings, cylinders or valve guides are the common causes of this condition. If the pistons and valve stems are not properly sealed, the engine will burn oil from the crankcase. Blue smoke is usually associated with engine wear and is typically found in older gasoline and diesel cars. Correcting the problem usually requires the service of a qualified technician.

Diesel Automobiles. No excuses. A diesel automobile that receives maintenance, in particular oil and oil filter changes at the manufacture's recommended intervals, should emit very little black smoke even under conditions of heavy acceleration.