I have a 2008 4.2L V6 with 64k miles that is idling rough. The vibration can be felt holding the steering wheel. It occurs whether in park or drive. After noticing the idle issue, I have cleaned the MAF and throttle body. Replaced the spark plugs and wires (Motorcraft Plugs and Autolite wires) and the fuel filter. There has been no change in the performance. It runs smooth when accelerating and I am not getting a check engine light. Should I replace the ignition coil? Am I likely feeling a misfire? I assumed if a cylinder is misfiring I would get a code. Please help with your thoughts. Thanks.

 

Have you checked your FPDM yet?

 

I would think that you have a vacuum leak. Lift the hood while engine is running and listen for a hissing sound. If you hear it, you can locate the leak by spraying carb or brake cleaner around the intake and listen for a change in engine rpm

 

If you changed your plugs and wires, you might want to go ahead and change your coil, too. A Motorcraft one is about $65 on Rock Auto.

 

Thanks for the ideas. Vacuum leak seems to make the most sense and I spent some time looking for a possible leak yesterday afternoon and did not find one. I can't hear a hissing sound so it is a needle in a hay stack. I'm going to test the coil and FDPM this afternoon. I am also thinking it could be nothing more than worn motor mounts. Thanks again. I'll post an update with what I find.

 

Not sure of the layout of the 08 v6, but my 99 has a vacuum line right below the throttle body that's a bit of a bitch to get at. That's where mine was leaking, took me awhile to locate it. Try there before throwing any parts at it. Good luck