2003 Oldsmobile Silhouette

Engine Mechanical problem
2003 Oldsmobile Silhouette 6 cyl Front Wheel Drive Automatic 109000 miles

My van was driving fine until I was in the drive thru car wash. Then the engine started running really rough and started making a knocking sound on the top of the engine. I scanned it and got a po300 code (random/multiple cylinder misfire). I changed the spark plug wires and spark plugs but this made no difference.
April 13, 2009.

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