The EGR valve is another suspect. A bit of carbon deposit can hold the valve open enough to cause surging and erratic idle.
The PCV valve is another possible trouble spot. This should be replaced periodically.
Another overlooked point of trouble is the vacuum line to the evaporative emmision system. Take a look at the hose going to the lower left portion of the radiator support.
Just a few ideas of places to look for potential problems.
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Sunday, August 9th, 2009 AT 9:22 AM