Low boost and hissing noise at Idle/low rpms

That spinning thing that makes all of the cool noises. OE and Aftermarket.

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asherudkinmtb
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Low boost and hissing noise at Idle/low rpms

Post by asherudkinmtb »

I have a bit of a problem with my 94 ej22t wagon. I lent it to a friend and when I got it back it was making no more than 5 lbs boost (it was making 15 before,) and it makes a slight hissing noise at idle and lower revs, past around 5k it goes way. Any ideas what it could be? I checked for a boost/vacuum leak with soapy water and carb cleaner and found nothing. maybe an exhaust leak pre turbo? Thanks!!
Legacy777
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Re: Low boost and hissing noise at Idle/low rpms

Post by Legacy777 »

Welcome to the BBS.

Do you have any modifications done to the engine/car?

It sounds like you're just getting wastegate boost and the boost controller isn't working. I'd check to make sure all the vacuum lines are hooked up properly and there's no debris in them. You can review the vacuum/boost diagram in the link below.

https://surrealmirage.com/vrg3/vacuum/

The other thing you may want to do is check the ECU for codes to see if the electronic part of the boost control solenoid is out of spec. You can also check the resistance of the solenoid to see if it's ok.

The factory manual has diagnostic info & how to check the codes in section 2-7.

https://www.main.experiencetherave.com/ ... and_Elect/
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
impostor
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Re: Low boost and hissing noise at Idle/low rpms

Post by impostor »

Do what Josh said, but don't limit vacuum leaks to just hoses. My 93 SS had a leaking injector seal on cylinder 4. Not the seal to the fuel rail, but the bigger one that seals the bottom of the injector to the manifold. Also check around the intake manifold gaskets
asherudkinmtb
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Re: Low boost and hissing noise at Idle/low rpms

Post by asherudkinmtb »

Hi,

Thanks for the replys!

Its got a few mods; TMIC, and manual boost controller are probably the most relevant. It has been throwing a code for a knock sensor, but it is a new knock sensor and my understanding is that this is a common issue with a rob 550 tune (it had been running fine with the code for over 2 months.) All the lines to the manual boost controller are intact and connected properly. After work I'll start pulling stuff apart and checking everything more carefully, but with a cursory carb cleaner check I still haven't found any vacuum leaks
Legacy777
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Re: Low boost and hissing noise at Idle/low rpms

Post by Legacy777 »

Use the factory manual and the wiring diagrams in there with a multimeter to check for continuity on the knock sensor wiring.
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
asherudkinmtb
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Joined: Tue Jan 03, 2017 6:28 am

Re: Low boost and hissing noise at Idle/low rpms

Post by asherudkinmtb »

I figured out the boost leak too, The tee was cracked and leaking, and I'll try that with the knock sensor.

I was so glad to have the boost leak fixed I figured I would drive it around for awhile and go do emissions, which I failed for HC and CO. So now I need to find a catted DP (I have catless with a race cat down the line) and re-test in the next week...UGH Emissions sucks I've never owned a car new enough to need it :D
Legacy777
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Re: Low boost and hissing noise at Idle/low rpms

Post by Legacy777 »

Make sure there are no codes in the ECU, reset the ECU, and make sure everything is running well before going to get the emissions done.

Try and drive vigorously to get the race cat heated up and see if that helps you pass.

Did you fail on the idle or high idle condition? What were the numbers?
Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

If you need to get a hold of me please email me rather then pm
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