Pop Noise from rear under car

[rakfint]

So, I need some diagnoses help.

When I start my car sometimes, i get a pop noise (not loud like a backfire) but more like someone knocked on the floorwell of the car. It also happens sometimes when I hit the gas hard or in a high gear.

I have only noticed this since I put a brand new muffler on to replace my old rusted out one.

Is this an exhaust leak of some kind, likely from a bad install of the muffler or possibly a leak somewhere else that has shown through now that the muffler is sealed tight?

Any ideas appreciated!

[WmWatt]

Check for loose connection. When the pipe is cold grab it and shake vigorously in every direction. Also check if it is close enough to hit anthing on the body.

[batstiva]

Also make sure all of the hangers are properly engaged. Had the same thing happen after a trip to Midas. Apparently they were only able to engage half of them. Not sure what the charge would have been to use all of them.

[Darlo]

Had this same issue when I got my pipe replaced the other day......They installed it somewhat crooked and it hit the metal part of one of the hangers........Just bend one of the metal brackets so it sits in the center of all the hangers when loose..........

[WmWatt]

When I took my Festiva back to a muffler shop after they'd done this the guy jammed a pipe between the tailpipe and chassis and pulled on it to shift the tailpipe. No more noise .