Rep Power: 0

Hello. I’m new to the forum, I may. It have this posted under the right heading. Anyway, I’ve owned my 2005 Honda Civic lx special edition for about 4 years now. It has the manual 5 speed in it. 240k miles. All stock. This morning on the way to work I noticed a horrible rattling noise when I let off the throttle while coasting down the road. As soon as I get back on the throttle is goes away. It does not happen at idle. If I rev it to around 2500 I can start to hear it but not near as bad as it is while going down the road. It does not sound like ears grinding and there is no noticeable difference in the performance of the car. I’m almost convinced I maybe bent the exhaust and now it’s hitting the bottom of the car after it heats up. I looked in the engine bay and under the car when I arrived at work and didn’t see anything obvious. I would appreciate some input.

 
Rep Power: 221

You need to get under the car and start smacking/shaking stuff to replicate the noise. More likely a heat shield than the actual exhaust being bent. Could also be a cracked manifold or loose/engine mount

 
Rep Power: 0

I am hoping it is just a heat shield. If it were a cracked manifold wouldn’t it be almost unbearably loud? I just can’t figure out why it stops when I am on the throttle. Theres a new pile of gravel at the end of my driveway and I may have backed into it too far and bowed the exhaust in the middle just a little. It def sounds like it’s right under the passenger seat but I noticed no heat there this morning.

 
Rep Power: 0

Did you figure out what it was? I have a 2013 Civic and thought it was the motor mount at first but the rattling for louder over night. Now it sounds like CV Boot or Axle so i took it to my mechanic, he told me to take it to the dealership because he thinks its an internal transmission clutch problem. It runs great. Just like you said though, as soon as I let my foot off the gas, its rattling clunking and it sounds like the CV boot problem I had once before on my 04 accord but my mechanic says no. I also have a A13 service code.