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Underboosting Evo 8

 
Old Feb 18, 2018, 03:48 AM
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Exclamation Underboosting Evo 8

Where should I start checking, here are the symptoms of the problem;
-MBC set at 20psi is now hardly doing even 18psi, mostly just 16.
- Idle AFRs read 11s and redlines to 9s rather than 14.7 to 11.4 (running rich)
- after letting of the throttle and the bov sets off, there is a slight hissing sound that comes. this sound is not from the bov as my bov has already set off by then and I am using a turbosmart recirculative valve.

I feel like this is a problem that has gotten worse because I was never able to exceed 22psi, dont' know why, I am on the stock 2003 evo 8 turbo..

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Old Feb 18, 2018, 05:14 AM
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Certainly a boost leak test is in order? (hissing sound)
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Old Feb 18, 2018, 07:42 AM
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check all vacuum lines esp those on the EGR solenoid behind the manifold. Check the lines on the turbosmart BOV and zip tie everything !!.

Then do the boost test. :-)
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Old Feb 18, 2018, 09:14 PM
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It's probably got something to do with this one?

https://www.evolutionm.net/forums/ev...smell-gas.html


Probably a hole in the intercooler.
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Old Feb 18, 2018, 11:11 PM
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Originally Posted by RightSaid fred View Post
It's probably got something to do with this one?

https://www.evolutionm.net/forums/ev...smell-gas.html


Probably a hole in the intercooler.
I changed that intercooler, got an 9 one
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Old Feb 23, 2018, 03:20 AM
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Boost leak
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Old Feb 23, 2018, 10:40 AM
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Boost leak almost forsure, do a boost leak test
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Old Feb 23, 2018, 11:07 PM
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Originally Posted by 4G63_EVO View Post
Boost leak almost forsure, do a boost leak test
getting it done today
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Old Feb 25, 2018, 02:47 AM
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Update

Update: boost leak test brought up bubbles at the throttle body, both sides where the shaft seals are located, getting both the throttle body shaft seals tomorrow and replacing them myself.

cant wait, pretty sure Iíve been losing a lot of power there
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Old Feb 27, 2018, 07:27 PM
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Make sure to put seals in freezer until you are ready to pop into place. Also, do not remove any of the black tar on back of throttle plate or you will have high idle.

Now for the weird 11 AFR of at idle. Idle isn't boosting, so there isn't any pressure to leak out. Unless the 11 AFR is with engine cold where it hasn't switched to closed loop. If engine was warm when you got 11 AFR, I think this will still be there. Hope I'm wrong.
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