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94 accord "resonance" @ 2000 rpm

hey there,

sounds like i may have a problem that is not all that uncommon
i have a 94 honda accord with 100k miles, runs great, handles great

just last week i noticed a resonant humming / growling sound coming from the engine - it’s very “vocal”
it only occurs around 2000 rpm, and is more pronounced when decelerating
there’s no apparent loss of power or fuel efficiency
the sound occurs with or without the transmission engaged and seems to be worse after the car has heated up a bit

cat converter? intake manifold?
any thoughts or direction would be great!

thank you!
~k

Many cars have tin heat shields attached to the exhaust system to prevent heat damage and grass fires…As time goes by, the spot-welds that hold them in place fail and they can make a lot of noise as they vibrate…

Many people simply remove them without any problems…Failed motor-mounts can also allow excess vibration to penetrate into the car body…

An accepted repair in my neck of the woods is to secure the heat shields with extra large worm-type hose clamps. It’s permanent and cheap.

However, the only way to know if this common cause is also your cause is to get under the car. It could also be an exhaust system rot hole beginning or even a rusty clamp or something of that sort.

Its either a Heat Shield somewhere along the system…SUPER SUPER COMMON…Or its the flexible downpipe from the header. I have also seen the heat shields actually attached to the bottom of the car vibrate and resonate also…Esp on THAT vehicle you have… I owned a 96 Accord for many many years…

Blackbird

aside from the damn noise - is it ever a serious cause for concern?

Sometimes it is. If the heat shields didn’t serve a purpose then they wouldn’t be there. Sometimes they protect other parts of the car. Sometimes they keep you from setting things like high grass or piles of leaves on fire. Go to any muffler shop. Ask them to find it and then ask what happens if you take it off or clamp it down. You might find that it can very simply be tack welded back on there for almost no $$.

IMHO it is a cause for concern.

The catalytic converter gets hotter than a match flame. They can and do light dry grass on fire. When they were first installed in cars grass fires were common. Heat shields were introduced in response to the problem, and in my opinion they ARE a safety item.