so i have this 04 accord runs fine but there is this rattling when parking in reverse and also there is this vibration i feel during the initial acceleration but smoothens out a bit but still noticeable.

 

I don't think this is going to end up being "Internal engine" so I'll move it over to General Tech where more people will probably see it and help.

Is it a 4-cyl or V-6 engine?

Can you get a helper so one person can put it in reverse and hold the brake, while the other looks and listens underneath? The first thing is to try to pinpoint the location of the rattling. Sounds like it might be the exhaust system rattling against the underside of the car. That can be caused by the engine movement when the engine mounts are getting worn or broken.

Weak engine mounts can also be responsible for the vibration. So if you can determine if one or more engine mounts are bad, you can replace them. If you aren't going to repair it yourself, you can at least have that knowledge when you ask the mechanic what might be wrong.

 

Motor or transmission mounts are likely.