2005 GMC Yukon • V8 AWD Automatic • 68,800 miles

05 yukon. Code p0300. Code0449
in addition. Low idle, about 600, so it idles slugish. Condensation out of tailpipe this morning was filled with carbon.
Check engine light has been on for a month, idling problems developed within the last week.
Any advice would. Be appreciated.
January 20, 2011.

The random misfire is coming from the PO449. That code indicates there is an EVAP vent valve control solenoid circuit is causing an issue. Based on your description, it sounds as if you age getting too much fuel to the engine VIA the EVAP system. Thus you have a sluggish idle and black sooty water coming from the exhaust. Have that checked.