97 accord, strange "ernnntt" sound

i have a 97 accord 2dr 5 speed that is making a stange "ernnnnnnttt"
sound, it only happens when i let the clutch out after a complete stop
or short shift and lug the motor a little,and only lasts for several
seconds. it sounds a little like a heat shield vibrating underneath but
i've looked and looked and can't find anything loose, so i suppose it
could be something in the driveline too. i tried to pinpoint it by
jacking up the front end and running it through the gears but it won't
do it when the wheels are just spinning freely. any ideas? thanks.

 

Try and determine if this sound relates to rpm - rev the engine slowly in
neutral. My guess is that it does. I used to have the same problem with my
Prelude and it turned out to be the baffles inside the exhaust system. A
slap with a rubber mallet cured it. However, when I got my 96 Accord, I
noticed the same problem but it was something completely different. It was
internal but closer to the engine. The Honda dealership stated it was
covered under warranty - for the life of the car as I had it repaired in
2002 for free by Honda. The problem then came back 2 years later but this
time it turned out to be the heat shield. The only way I figured it out was
to get under the car while running and someone operating the gas. Try this
course first.