Prowop

I have a 98 civic with 200k on with auto transmission. Just yesterday i drove my car and it was fine. As the day went on running my errands, a noise developed. It sounds almost as if I could have a hole in my muffler. Strangely enough, this noise does not sound when going in reverse. If coasting ( foot is not on gas pedal) it also will not make a sound. My girlfriend said it seem to have stalled on her late last night. What could it be?

Prowop

Also there is no check engine light on.

J-Master Flex

You could possibly have a clogged catalytic converter, forcing the engine to work harder on acceleration. I would say your best bet would be to look under the car, check the whole exhaust from the manifold back all the way to the muffler, and rev the engine a few times to see if you can pinpoint where the noise is coming from.