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2007 Mercury Milan Question: PO420 code



, 3.0L V6, Lees Summit, MO, September 10, 2012, 19:17

Car has 82,000 miles. Replaced battery and one month later emission light came on. Codes PO 305 and 301 cylinder misfires came up. Replaced all 6 spark plugs and 6 ignition coils and intake gasket. Cylinder 5 kept misfiring and burnt out the engine control module so replaced that also. One week later emission light came on again and now have a PO 420 code. Other than replacing catalytic converter is there anything else it could be

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    Greg's Orange Auto (15380 Answers) , Orange, CA - (714) 361-9386
    globalhelper September 10, 2012, 23:07

    i think you need to seek help the misfires poss burn't catt out. the po420 could be a couple of issues.like catt ,o2 senors or exh leaks

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