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Humming noise when accelerating


I am trying to diagnose a sound that is coming from my 2001 Camry 2.2L. When I accelerate there is a load humming noise coming from the engine. It happens at all speeds and only when I accelerate. Any thoughts? Thanks

If “at all speeds” also means when standing still then pop the hood, rev the engine and listen. Try to get an idea of where the noise is. I’d start my guesses at the exhaust system - depending on exactly what that humming noise sounds like.

When you accelerate your engine is normally twisting a very small amount within the confines of the engine mounts. It is possible that either the engine or the exhaust pipe is touching something at that time. To begin, look for a heat shield that is very close to the exhaust.

Hello and thank you for your responses. I finally had time to have my wife rev the engine when I was underneath and I have found that the noise sound like it is coming from part of the muffler system, underneath the engine. After looking on the internet it looks like it is the catalytic convertor. It looks like a bunch of wire that is woven together like a basket. There is also signs that it has rusted out.

So, with that info how hard is it to change myself? It didn’t look like it would be all that difficult. It looks like a couple of bolts on either side.

That’s not the cataytic converter but instead the exhaust flex pipe. All you need to know is the length and diameter and you can order one from here.


My own $.02 in terms of changing this yourself is that if you could you probably wouldn’t be asking. What is your level of mechanical ability? Tools?

The issues have to do with all of the rust & heat - these things practically become welded together; there’s often not much room to work; it probably has to be done from underneath. Do you have access to a lift (best)? Or at least jack stands or a set of ramps?

If you can get the car up in the air safely and have decent mechanical ability and maybe access to an angle grinder you may be able to swing it.

But then again, I had one changed out but it is welded inline in the pipe. So it had to be cut out & a new one welded in. I paid all of about $150 at a muffler shop.

Great information from everyone. Thanks. I consider my knowledge to be intermediate, I find working on the car to be fun and do it more as a hobby and to save a $ here and there. I have never had to do anything with a muffler before. It does seem doable but I have given my shop a call to see what they would charge. If it is $150 that is worth not screwing somethign up. I will let you know the outcome. Thanks

I realize that this thread is really old, but, I am having the same issue. Did you ever figure out what the problem was?

One reason why this would happen with any car is, if your number place (license plate) is loose. Especially if you just secured it only top two screws it will vibrate and touch the body of the car while driving and thus making humming sound due to vibrations. With acceleration the frequency of vibration of number plate increases and thus the sound increases.
Secure the number plate and the problem will go away. However if your number plate is already secured then there could be some other issue. Hope this helps.

Not the plate . It was the exhaust system and since it was first reported in 2011 I think it has been fixed.