For starters I have a 2001 protege with the 2.0.

So, I started noticing a slight engine squeal after driving for awhile. Car would start and run fine, with no engine noise. Then I would notice the engine would squeal with throttle. I thought it might be transmission, so I changed the fluid. No help.

Then the squeal started getting louder, and power started dropping. It was noticable when I started the car. Everything pointed at belts. So I disconnected the alternator belt, and ran the engine. Still a squeal. Did the power steering pump belt next. Still a squeal.

So I replaced the timing belt as it was over by 5k miles anyways. Guess what...still a squeal. I am at my wit's end with it. Any suggestions would be appreciated.

 

I have this same thing happening to me on a new car I just bought and I’m worried it’s something serious

 

Intake system air leak?

Low engine oil?

Low coolant level?

 

Sorry I never posted the update. One thing I failed to mention was that the car had over 300K miles on it. I ended up placing the car on jack stands and had a buddy advance the throttle while I listened under the car. I eventually found the squeal was coming from the mani-verter. Once I removed the mani-verter, I saw that it was blocked almost solid. I made some modifications to it while I waited on a new one to come in from Rockauto. That fixed everything. The squeal was gone, power and economy picked back up. It was almost like it had a fresh engine in it.