I have an automatic 2010 mustang with the 4.0 v6 sitting right at 100k miles. I have a problem where the rpm’s constantly wobble. It constantly goes up and down by about 100 Rpm never stopping. You can feel the car idling rough and it feels low on power. I’ve taken it to several shops and everyone tells me it’s normal but the car never did this before. The power train control module has been replaced, the car has new spark plugs, new plug wires, a new coil pack, and a new fuel filter. Please help. Thanks!
Any codes?
Also check all of your vacuum lines & vacuum operated accessories. A small leak can do that.
There are no codes. I was thinking a vaccum leak as well. Thanks.
Try a new PCV valve - Motorcraft #W0133-177203. Your old one with 100K miles is probably malfunctioning. This is the OEM part but after market valves are available just about everywhere.
