I’ve got a 2007 Cadillac CTS with the 3.6L engine. The car has begun idling rough when stopped at lights, parked, etc. A few days later, it also began starting reluctantly. The rough idle varies in intensity, but is almost always present. The CEL is not illuminated and the car seems to run fine when not idling.
A few months ago, the car began running like a lawn mower and the check engine light came on. It turned out to be a misfiring cylinder. I had all the plugs replaced along with the ignition coil for that cylinder.
The car ran great for a few months after the repair, but now this rough idle problem has appeared. Has anyone experienced this with a CTS? Do you think it’s related to the repair a few months ago? Any suggestions?