EVAP, an abbreviation for fuel evaporation control system, prevents gaso­line vapors from escaping into and polluting the atmosphere. When an EVAP system sustains damage, an engine can idle roughly and/or stall, and there will probably be a strong odor of gasoline.

The heart of the EVAP system is a charcoal canister that absorbs va­pors, which enter the canister from the fuel system through hoses. As the engine runs, vapors are drawn into the cylinders and are burned. The performance problem and odor of gasoline arise if the can­ister cracks, if one of the hoses is damaged, or if a filter inside the canis­ter clogs.

Here is how to repair a vehicle’s EVAP system:

• Find the charcoal canister.
• Using self-adhering labels, identify each hose in terms of the can­ister fitting to which it is connected. Later, each must be reattached to the correct fitting.
• Loosen clamps and pull off hoses.
• Loosen the bracket holding the canister, and remove the canister from the vehicle.
• Inspect the canister for damage. Pay particular attention to the area around hose fittings. If you find a crack, take the component to the parts department of a dealer who sells your make of vehicle and buy a new one.

• Turn the canister over to find out whether it has a filter, which should be replaced before you reinstall an undamaged canister.
• Inspect hoses and replace any that are cracked.
• Install the canister and connect hoses to their proper fittings, mak­ing sure that clamps are secure.

If this fails to solve the performance prob­lem and to eliminate the gasoline odor, replace the canister. A canister without a filter has an estimated life expectancy of 50,000 miles.