Sudden loss of power - Engine problem? Drivetrain?

Hey all, my first post here,

I've recently come into a big problem with my 2008 Legacy 2.5i and was wondering if anyone had some insights into what might be wrong.

The situation:

One night, while driving at regular highway speeds, 100-110km/h (60-68mph), I tried to accelerate and noticed that I was going nowhere, and rpms were going up much slower than usual. I thought this was awfully strange so I did some tests and here's what I found. The car is automatic with "sportronic" shift or whatnot.

Highway speeds -

3rd gear - I was able to make my way up to 120km/h, although it took a long long time. Past 4000rpm, the car began to make a grinding/rattling type of noise, which sounded like came from the engine bay.

4th gear - Once I hit 120, I tried shifting to 4th. The car was suddenly unable to maintain its speed and began deccelerating to 100-110, and was unable to go past 2000rpm .. but I was still able to cruise. Back to 3rd gear, I think, at least there's SOME power there.

3rd gear - I decide to go down to the 80-90km/h range (50mph-ish) and see what's up. I notice that power comes on and off - even though I'm keeping a constant throttle. It takes me ages to get back up to 110, even if I floor the accelerator.

Time to get off the highway .........

City speeds -

1st gear - From a standstill, from 0 - 1500 rpm, there is almost no power or acceleration. Power still comes on and off. From 2000-4000, there is a decent amount of acceleration, but it comes and goes. Past 4000, the grinding/rattle is still there.

2nd, 3rd - Pretty much noticing the same low-to-high end characteristics as 1st gear.

4th - is able to go from a low rpm, up to 2000rpm, but just like the highway, it won't go any higher. At lower speeds, at least its able to speed up my car, instead of slow it down.

I also notice a weird feeling while idling. It's difficut to explain it, but if you think of a normal idle as a consistent 4 "beats", the idle now feels rough and uneven.. like it goes "one - two - three - fooooour - one - two - three - foooour", with a low long drawn out fourth "beat".

Also this may or may not be relevant (afraid it might be) but several nights before this happened, I was driving an heard a sudden loud noise that came from the front-right of the car. It sounded as if I might have run over something plastic (though I didnt see anything on the road), or a rock may have got kicked up into the wheel well (but I pulled over and took a quick look and didn't notice anyhting different. If it was related, it's quite a delayed reaction that the car had to it......

Anyways, long post but I hope it's detailed enough that someone here might be able to help out!

Dead injector or ignition coil are the first things that comes to mind.

Otherwise it may be a problem with the fuel pressure, which probably means that the fuel pump or filter may have a problem.

Also check the air intake so you don't have any inhabitants there - like squirrels, rats or similar.

And finally - a compression test may reveal if there is any mechanical problems with the engine. The spark plugs may also provide additional information. Oil on the spark plugs are bad.

Notice that if there are problems with the injectors or ignition it may cause harm to the cat.

But be aware that this may be a warranty issue, so check with your dealer.

Dead injector or ignition coil are the first things that comes to mind.

 

Otherwise it may be a problem with the fuel pressure, which probably means that the fuel pump or filter may have a problem.

 

Also check the air intake so you don't have any inhabitants there - like squirrels, rats or similar.

 

And finally - a compression test may reveal if there is any mechanical problems with the engine. The spark plugs may also provide additional information. Oil on the spark plugs are bad.

 

Notice that if there are problems with the injectors or ignition it may cause harm to the cat.

 

But be aware that this may be a warranty issue, so check with your dealer.

Thanks for the advice! I checked with my dealer, and just recently got my car back. They had to send the car to Subaru Canada to figure out what the problem was! Apparently the baffle in the catalytic converter shifted, blocked the exhaust, and the resulting back pressure caused the loss in power? Just posting the solution in case anyone faces the same scenario!