Hmmm...a 3 year old car huh...
Automobiles use vacuums to adjust and control various engine components. A leak in a vacuum hose will cause a loss of vacuum power that might result in a high idle. Check vacuum hoses (thin rubber lines) for cracking or other damage. Hoses often are damaged where they connect to solid components.
Clogged PCV Valve
A PCV valve is used to vent exhaust gases that have leaked past the cylinder rings into the engine block. The gases pass through the PCV valve and are routed into the engine's air intake. A clogged or broken valve will stop this flow of air, which can cause a high idle.
The oxygen sensor detects the amount of oxygen in the exhaust. This data is used by the engine's computer to adjust the mixture of air and fuel used for combustion. When the oxygen sensor begins to fail, the information reported to the computer is slowed or inaccurate. The computer might then set the mixture too rich (too much fuel), resulting in an idle faster than needed.