Harsh idle with rattle

Hi everybody. I have a 2014 US Mirage 1.2 CVT with 94k miles. All of a sudden, the car has developed a harsh vibration while idling, with a noise like a loose heat shield or similar. The noise gets worse as you add load to the idling engine, such as A/C, or accelerate more aggressively. I also tried putting into drive with the parking brake on and AC on and that really makes it rattle. As the RPMs increase the issue smooths out and quiets down again. I can't seem to find an exact location where the rattle is coming from. The engine's performance seems normal.

To me it seems like a torn engine mount causing excessive engine block movement and vibration, resulting in noise and harshness. I had someone add and remove load from the engine while I looked at the engine mounts, to see if I could see excessive slack indicating a torn mount. It seemed as though the passenger side mount was pretty sloppy, but it is a metal can with a stud sticking out, so I can't inspect the internal rubber for damage. Besides, an engine that vibrates this much from the factory may have sloppy mounts to try to contain it anyway, so I'm not certain I've found the issue.

Anybody else had this issue or similar? Thanks.

I assume you have no check engine lights or anything else that would indicate a malfunction with the engine?

Hello kzp700. Thanks for signing up and joining our community, and welcome to the forum.

From memory, reports of noise from other forum members have included:
1. Snorkel to airbox joint getting worn thin (fixed with tape) and
2. Exhaust hanger rattling (hanger was taped to prove the cause, then replaced.)

Hope that helps. Please be sure to share your findings as it will help others down the road.

Two things I've seen cause a vibration like that in these things are gravel getting stuck in the subframe and wedged behind the engine-subframe mount(the one on the bottom that stops it from rocking front to back). The other one was when the car was bottomed out on something, one of the exhaust hangers came off and the front of the exhaust was resting on the subframe.
One other thing I've seen was the heat shield on one of the cats came loose, I just pulled it off.
I'd check those free things first before throwing random parts at it or the "take your car to a dealership cause they know your car" comments appear.

I guess heat shield without having anything more to go on.

No check engine light. I did take the snorkel off and took some slop out of the air box, which did reduce a lot of noise, but was not the the cause. Thanks for the suggestions, I will check those out ASAP and report back.

Got it figured out. Thanks for the hints, you guys got me pointed in the right direction. Turns out it was the exhaust hanger. Made the catalyst start banging against the back of the engine bay, but the squeaky sheet metal rattle sounded more like a slipping belt than anything else, and all that racket was coming from around the engine block, so never would have thought to look halfway down the car to find the problem. But, there it was, stupid pipe hanger had fallen out. After I fixed it, wife said she was loaded up with passengers and hit a rough railroad crossing, so that must have been what knocked it out, but I've certainly not seen that before.

Quote:

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Originally Posted by kzp700

Got it figured out. Thanks for the hints, you guys got me pointed in the right direction.

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And Thank You for reporting back on the fix. That's what forums are good for.

So - what's next for your Mirage, now that that's taken care of?