# Rattling noise in park and upon acceleration **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** mercury, grand-marquis\ **Created:** [March 2, 2023, 10:04pm UTC](https://community.cartalk.com/t/rattling-noise-in-park-and-upon-acceleration/189413 "2023-03-02T22:04:50Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Todd58](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/todd58/32/17237_2.png) [@Todd58](https://community.cartalk.com/u/Todd58)\ **Post date:** [March 2, 2023, 10:04pm UTC](https://community.cartalk.com/t/rattling-noise-in-park-and-upon-acceleration/189413/1 "2023-03-02T22:04:50Z")
When the vehicle is idling in park, there is a rattling sound coming from underneath, somewhere near the middle. When I put it in drive or in reverse and just start to accelerate, it gets louder. Then it goes away once past the point of just giving enough throttle. It almost sounds like a big rock or bolt is rattling in a pan. But it only does it at low rpm’s. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [March 2, 2023, 10:14pm UTC](https://community.cartalk.com/t/rattling-noise-in-park-and-upon-acceleration/189413/2 "2023-03-02T22:14:13Z")
Ask your shop to put it on their lift. Then someone above can start and idle the engine, and someone underneath can listen for where the sound is coming from. That’s where to start imo. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [March 2, 2023, 10:16pm UTC](https://community.cartalk.com/t/rattling-noise-in-park-and-upon-acceleration/189413/3 "2023-03-02T22:16:08Z")
There might be a loose exhaust heat shield. Tester ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [March 2, 2023, 10:16pm UTC](https://community.cartalk.com/t/rattling-noise-in-park-and-upon-acceleration/189413/4 "2023-03-02T22:16:38Z")
Is this the same noise you asked about in August of 2019 ? Did it go away and now come back ? ---
**Author:** ![Todd58](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/todd58/32/17237_2.png) [@Todd58](https://community.cartalk.com/u/Todd58)\ **Post date:** [March 2, 2023, 10:25pm UTC](https://community.cartalk.com/t/rattling-noise-in-park-and-upon-acceleration/189413/5 "2023-03-02T22:25:19Z")
Different noise. That noise was the catalytic converter. ---
**Author:** ![Todd58](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/todd58/32/17237_2.png) [@Todd58](https://community.cartalk.com/u/Todd58)\ **Post date:** [March 2, 2023, 10:27pm UTC](https://community.cartalk.com/t/rattling-noise-in-park-and-upon-acceleration/189413/6 "2023-03-02T22:27:17Z")
I was thinking a loose shield. I probably need to get it on a lift and tap around. I just replaced the transmission seal because it was leaking. Thought that also was the problem. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [March 2, 2023, 10:53pm UTC](https://community.cartalk.com/t/rattling-noise-in-park-and-upon-acceleration/189413/7 "2023-03-02T22:53:42Z")
I agree with Tester, sounds like a heat shield… But it could also be the cat converter going bad again _ **if** _ you bought a cheap one… I’ve seen a lot of “universal cats” only last about 13 - 14 months…