1. Running Right - Do not subject your vehicle to a smog inspection if it does not run right. Chances are that it will fail the smog check and you will lose your inspection fee. Seek repair assistance first. This will save you time and money, and ensure your vehicle will pass the smog test.
2. Take a Drive - Drive your vehicle for at least 20 minutes prior to arriving at the smog station. This will ensure your vehicle is properly warmed up and is running at it's optimum level. Remember your engine is a fuel burning machine. To ensure proper combustion it needs to have sufficient time to warm-up and this can be accomplished through driving for at least 10 to 15 miles.
3. Use Additives - The use of fuel additives can be very helpful in lowering emission levels and helping your car, truck, van or SUV pass the emissions inspection. Fuel additives are generally poured into a vehicle's gas tank during fuel refueling. The additive is mixed withyour vehicle's fuel. The purpose is to clean carbon deposits within your engine's intake and exhaust paths, allowing for both fuel and air to flow freely within its passages, thus lowering emission levels, improving combustion, increasing overall engine performance, and helping you pass the emission test. These types of products offer helpful solutions to various vehicle emission and smog test problems.
Note: Read your fuel additive's instructions regarding having your vehicle smog tested while using the additive. Fuel system additives and fuel system treatments require using the complete application and refueling with fresh fuel prior to the smog check.
4. Inflate Tires - If your vehicle is model year 1999 or older it will be driven on a dynomometer while a sample of its exhaust is collected by the smog machine. Making sure your vehicle's tire pressures are even and correct will allow the vehicle to be driven with greater stability and accuracy during the smog exam.
This will improve the overall emissions output of your vehicle by allowing the engine to maintain a constant and steady load. Correct and even tire pressure may be the deciding factor between a borderline vehicle failing or passing the smog test. This passing tip, as well as tips number 5 and 7 do not necessarily apply to your vehicle if it's 2000 model year or newer; this is not to say your vehicle's tires shouldn't be properly inflated, of course.
5. Change Oil - If it's close to your next oil change interval, go ahead and do it before the smog check. The PCV (positive crank ventilation) system of your vehicle is designed to allow your engine to breath fumes located in oil compartments (oil pan, ect.). The fumes are then burned through the combustion process. If the oil in your engine is contaminated due to inadequate oil changes it may very well cause your vehicle to fail the inspection.