[ledzeppelin240]

The HC emissions are controlled by the EVAP system, PCV Valve, Air Pump(Air Induction Valve) and believe it or not the Catalytic Converter. The ignition system is what usually causes high HC levels, because there is excessive unburnt fuel.

Air filter, fuel filter, condition of the fuel system, spark plugs, spark plug wires, distributor cap and rotor, and regular oil changes also contribute to your emission levels.

Some tips that I found in a book I have are:

1. Test your vehicle on a nice day. Cold weather requires that the engine run longer for the engine to reach operating temp.

2.Battery must be in good condition. A weak battery causes fuel-injected engines to run too rich.

3.Change engine oil before having the vehicle tested. Dirty or contaminated oil increases exhaust emissions.

4.When fueliing your vehicle, do not overfill the gas tank, cause then liquid gasoline can be drawn into the engine throught the canister purge system.

5.Using premium-grade gasoline helps prevent NOx emissions.

6.Drive 20 minutes before the vehicle is tested to ensure that the engine oil, coolant, and catalytic converter are at normal operating temp.

7.While waiting for the inspection run engine at a fast idle. (Hmm..???)

8.Make sure your A/C, heater, and defrost is all off preventing extra load on the engine.