turbobuick86

2014 V6 with 40K miles. Completely stock.

Wife complains of rattle towards rear of car, I go out start the car, and can plainly hear an annoying rattle with car idling in the driveway. The mufflers are both rattling occasionally, not constantly. After a few minutes of scratching my head, I turn the AC off and presto!, the rattle completely stops. When the ac compressors kicks on and off, the rattle goes on and off. It the initial extra load on the motor, the ac sends a vibration through the motor, through the head pipes, through the exhaust and rattles the mufflers. The ac cycle, I'm guessing is 15-20 seconds?

Now I can rap the bottom of the muffler with my fist and they both rattle with the car not running. First of all, is this normal or are there loose baffles in both mufflers? $400 would get two replacement stock mufflers, but I need assurance this would fix the issue. Believe me when I say I've checked all the hangers, clamps, and assorted hardware. I'm leaning toward the mufflers are junk.

The motor idles at approx 650-700. I don't see any fluctuation with the AC on. I don't see an easy stop screw to adjust the idle, guessing it's all programmed. I was imagining another 100 rpm might cure the momentary vibration.

Everything about the car seems normal and it's really been a great car other than this weird issue. If you have any ideas or thought, I'd appreciate input.
Thanks!

Bert

normally there should be no rattle; and since you already checked the hangers, etc. I am leaning toward the muffler itself also

suggestion: check your local Craig's List for take-off mufflers, they can be found super cheap when people upgrade their mufflers and they want to get rid of the old ones

turbobuick86

I finally took off drivers side muffler and it rattled like a can of marbles. Ordered a set of Ford Racing by Borla mufflers.