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2000 impreza rs Hissing sometimes at medium to full throttle, loss of power during this.


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Hello, I have searched and searched for an answer, and I have went over a lot of "could-be's" on what's going on with this. I'm hoping someone can help shed some light on this.

 

So, its a 2000 model Impreza RS 2.5 N/A, with manual transmission. This is the MAP sensor engine, not the Mass Airflow version. The engine seems to run good, and I can't hear the hissing at idle, or by revving the car when sitting (unless I was driving and it started hissing, which, then I can put the car in neutral, rev it, and it will hiss still). It's complicated to explain, and it doesn't do it all the time either.

 

It started after I changed my rack and pinion due to a faulty ring gear (is that what they call it?). I had to undo the exhaust from the heads and the collector in front of the first catalytic converter (one bolt near the first cat was impossible to reach, so I had to undo the one I could get to, and just try to swing it out of the way). So, rack and pinion replaced, I put the exhaust back up, gaskets back in, and tightened it all down. 

 

I test drove the car, and it seemed fine, but then I was trying to merge, and I downshifted, and gave it some rpm's. I heard a loud hissing noise from what I expected to be the driver side of the engine bay. Along with this, there was a lack of power (rpms increased, but it didn't feel like it had much power, and the rpms were increasing slower than when it isn't hissing). Now, I remember there was the power loss feeling randomly before this, but now I definitely feel it only when the car hisses. 

 

I decided it sounded like a vacuum leak, so I set out to start checking all vacuum hoses..ended up breaking a nipple off the purge solenoid valve under the intake manifold. So, I repaired that. Still hissing randomly. I started trying to trace all vacuum lines. I eventually found a torn hose and replaced it (I'll post the pic of that from my phone when I get a chance). I believe that one was one of the three hoses over at the fuel filter area near the brake master cylinder in the engine bay, but still, it's hissing and lacking much power when this happens. 

 

I've wondered about the previous owner using clear blue hoses to install the CAI (the hoses go from the intake to the valve covers, and the splitter between the pcv and intake manifold... can post pics of that too, later.). They don't seem to squish, but I'm wary of cheap hoses. I'm trying to get it solved, since it is very irritating. It does SEEM to have a low operating temperature idle of 600ish rpms. Here is the link to the video of it. Listen to the whole video, you will definitely hear it.. 

 

<div style="position:relative;height:0;padding-bottom:75.0%"><iframe src="https://www.youtube.com/embed/xZ1ADxFS13Q?ecver=2" width="480" height="360" frameborder="0" style="position:absolute;width:100%;height:100%;left:0" allowfullscreen></iframe></div>

 

Thanks in advance for any and all suggestions/help/advice!

 

EDIT: Also, I forgot to mention, I had a CEL for p0420, and I know the front oxygen sensor isn't working via using an obd link to monitor the sensors. The rear one works, but the front gives a 0 reading at all times, like it just doesn't work at all.

Edited by Subardoo
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Sounds more like an exhaust restriction to me. Back pressure is building on hard acceleration and is forcing its way out through a leak somewhere in the exhaust.

Loosen the bolts at one of the flanges so you have a small gap between the pipes and take it for a quick drive and see if it still has the power loss.

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GeneralDisorder, thanks for the reply! I forgot to mention, new air filter has already been installed and it continued the hissing.

 

Fairtax4me, thanks for the reply! I'll give that a shot and see what happens. I suppose it won't hurt anything, since the front oxygen sensor isn't working anyway.

 

I'll be back with results later.

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double check the 'bottom' of the air filter box - both my cars have broken slots wher e those tabs go. (right now, I have zip ties holding the box halves together)

 

Even before they were broken, easy to misalign the box after a filter change.

 

vacuum gauge testing might be a good idea.

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Okay, the results from the cat disconnect... Loud as hell hahaha. But I can't really tell any difference.

 

1LuckyTexan, thanks for the reply! I dont have the factory air box, previous owner had installed a cold air intake, and I double checked the clamps. All are tight, and the hoses dont seem to be busted. I guess the next step is vacuum testing.

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Okay, the results from the cat disconnect... Loud as hell hahaha. But I can't really tell any difference.

 

1LuckyTexan, thanks for the reply! I dont have the factory air box, previous owner had installed a cold air intake, and I double checked the clamps. All are tight, and the hoses dont seem to be busted. I guess the next step is vacuum testing.

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Okay, the results from the cat disconnect... Loud as hell hahaha. But I can't really tell any difference.

 

1LuckyTexan, thanks for the reply! I dont have the factory air box, previous owner had installed a cold air intake, and I double checked the clamps. All are tight, and the hoses dont seem to be busted. I guess the next step is vacuum testing.

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Okay, the results from the cat disconnect... Loud as hell hahaha. But I can't really tell any difference.

 

1LuckyTexan, thanks for the reply! I dont have the factory air box, previous owner had installed a cold air intake, and I double checked the clamps. All are tight, and the hoses dont seem to be busted. I guess the next step is vacuum testing.

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Okay, the results from the cat disconnect... Loud as hell hahaha. But I can't really tell any difference.

 

1LuckyTexan, thanks for the reply! I dont have the factory air box, previous owner had installed a cold air intake, and I double checked the clamps. All are tight, and the hoses dont seem to be busted. I guess the next step is vacuum testing.

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Thats what it sounds like, hissing. You can hear it in the video. Its crazy. I dont think it did it any since the testing. Haven't gotten to really drive it a lot since then, though. I'm gonna go test it again shortly since the weather is good. But also, since you mentioned it...I'm gonna check my brakes/calipers as well! I have heard a small, quiet noise coming from the driver side wheel, and it sounds like a small bird chirp or tweet here and there.

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put a hose to your ear and carefully move it around in the engine bay to locate the area it's coming from? check for a crack at the Y pipe on the exhaust.

 

try a vacuum gauge test - get it on loan from a parts store, check on-line for guides of all the stuff it can show.

Edited by 1 Lucky Texan
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Just wanted to give you all an update.

 

I took the car out and tested it, and at one point, the loss of power and hissing started, and I decided to push through the loss of power and hissing.

 

"It's gonna go, or it's gonna blow!" lol...That's about how I felt at that point.

 

The car got a little more noisy, but appeared to get better finally. So, the next day, I got under the car again, and hit everything exhaust-wise with a rubber mallet.

 

You could hear the rattle inside the exhaust.

 

I haven't heard the loud hissing anymore, though there is still a small hiss (which is nowhere near as audible), but no more power loss. 

 

So I guess that's what it was. The converters were clogging. Probably just weren't fully clogged, I got the car, then it finally decided to clog up enough. 

 

My check engine light is no longer working now, but before all of this, I did have a p0420 code, so maybe that had something to do with it.

 

I hooked up an obdlink lx bluetooth unit to the connector, and the front o2 sensor isn't even giving a reading.

 

That's next on the list, and then all rear bushings need to be done. 

 

Thanks everyone, for all the assistance, help, advice!!

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