The car was made road ready 5 years ago. It was a trade in so it sat only for installation of tires,oxygen sensor,plugs & wires and perhaps a few other replacement parts.Recently the throttle body was cleaned. I was told the plugs were fine,but I'm not sure when they were last changed.The check engine light is on after the car has been warmed up,idling or warmed up in winter.Fluids are checked frequently,oil & filter changed as needed.It runs fairly well for the age and mileage.No fluids leaking,private property parking so car could be moved other placed to check for leaks.What could be causing the misfiring at various speeds and engine light after warming of the engine?
What makes this problem better or worse?
Worse when engine is warm.
How long has your 1991 Mercury Topaz had this problem?
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