Volkswagen and Audi 1.8L turbocharger engines with codes for a misfire: PO300, PO3010, PO302, PO303 and PO304. These codes or often caused by the individual (coil-on-plug) ignition systems. Symptoms other than a check engine light would include loss of power, poor throttle response, misfire (bucking) and vehicle engine shutting off.
In most conditions, a misfire (engine bucking) will point to a component of ignition system- spark plug, coil or wiring. Volkswagen and Audi vehicles with the 1.8L turbocharged seem to have problems with the coil-on-plug ignition systems. Most likely the excessive heat causes the ignition coil and/or the harness to become brittle and cracked leading to engine misfires or failure.
Vehicles w/ 1.8L turbocharged engines...
2006-2001 Audi A4
2004 Audi A6
2005-2003 Audi Allroad Quattro
2006-2005, 2002-2001 Audi TT
2005, 2001 Volkswagen Beetle
2005-2000 Volkswagen Golf
2004-2001 Volkswagen GTI
2005-2001 Volkswagen Jetta