I'm hoping to get a little input on a misfire in my girlfriend's car. It is intermittent. On a cold start, there are no issues. When the vehicle turns off, or returns to a lower rpm, the CEL starts blinking, and you can feel the engine shudder. Every now and then, there's a small backfire through the exhaust, it seems. Vehicle Info: 2009 Mercury Mariner AWD with 3.0L V6 Codes: Cyl 4 Misfire, Cyl 4 Injector Circuit, Bank 2 Lean This afternoon, I switched the #4 and #5 coils around and checked the spark plugs. They are worn, but the color is good. The test drive yielded no changes. The same codes came back after being erased. I would say, at this point, that the #4 injector is bad, or has issues when it is hot. Has anyone had similar issues with other Ford vehicles, or maybe solved a similar issue? Thanks.