intermittent engine miss

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Hello: I have a 1998 Cadillac Deville (base) with a 4.6 engine. The engine is starting to miss intermittently mostly noticed during idling in drive. Have owned for 2.5 years. Has over 130,000 miles and have never changed fuel filter or spark plugs or wires since owned. Have never used injection cleaner. There is no service engine light on. When accelerating seems fine. What could be the cause or better yet what course of action should I take? Please respond at: zynnis@yahoo.com Thanks Donald Whitehead