Get this...

I bought an 05' EVO 8 about 3 months ago. I noticed, when I am part throttle, it would build and hold boost fine, but as soon as I go WOT, the boost rises, hits 20, and then falls all the way back down to about 4 or 5.....you can hear it...vroooom pssssss....just leaks all the way down. I had yet to solve this problem...until tonight.

I drove to work this afternoon, it drove normal. I get in the car and pull off, and the bov flutters when it dumps...I was like man, that's weird(I can make it make this sound if I'm boosting and let my foot of the pedal slowly) so I kept driving and now it's doing it EVERY time it dumps. Like all of a sudden, it makes the fluttering noise on its own without me doing it a certain way to generate that same sound.

AND ON TOP OF THAT...I go wot and full boost it, and for the first time since I owned the vehicle it held all 20lbs, until I was ready to stop.

Did magic Mitsubishi gnomes fix my **** while I was at work?

Or am I somehow doing damage to something...the reason why I decided to make a post now, is because i'm driving to Florida this week(10 hour drive) and want to know if I should expect any surprises.

Thanks for your timely responses, I leave Friday...

 

Vaccum leak or bad BOV. Is it stock 8 bov?

 

It's a Synapse

 

Do a boost leak test,and go from there with fault finding.

 

What would that tell me? I know the boost leak issue has something to do with the diverter valve, I just need to figure out 1)why the weird stuff happened, and 2) is it safe for me to drive on an upcoming road trip...

I'm assuming/hoping it is ok, but i'd like your opinions as well

 

A boost leak could come from a lot of places.Clamps that aren't tight or even from throttle body shaft seals,or intake mani vacuum hoses.If you pump the air just listen to where it's coming from or even spray soapy water where it's coming from.

 

I found the boost leak, it's the BOV. It's malfunctioned somehow and plugged the leak I use to have. Like I had a leak, and the BOV sounded like it operated normal, now it flutters, but the leak is gone. It holds perfect now

 

Good stuff,glad you sorted it out.

 

I can't tell if you're confused about what i'm saying lol. I still have an issue here...

Something happened that I didn't have anything to do with, and after months of leaking, all of a sudden the bov changes sound completely and the pressure doesn't leak any more...

I went to work leaking boost with a "GUSHHHH" bov sound...and when I left work that night, it made the flutter sound and wasn't leaking any more. It's still making the flutter sound now all the time. I didn't touch anything...lol

 

Try somebody else's BOV and see if that eliminates the issue.

 

So I would recommend that you follow the instructions in this thread.

https://www.evolutionm.net/forums/ev...g-how-why.html

Most likely there are other variables at play. Now would be a good time to start working on your Evo and properly isolating them before some more damage occurs.

 

I'm having a similar issue with my 05 MR. It will build boost and hold fine at part throttle but at WOT in 3rd or 4rth gear it will taper to about 1-1.1 bar. If I'm in 5th gear it will hold 1.3-1.4 bar at WOT. Is this a boost leak or just the WGDC variations by gear. If it was a boost leak wouldn't it be consistent no matter what gear? This is what I can't figure out.

 

Sounds like the BOV is stuck closed. The sound you are hearing is compressor surge.

 

Wait a minute, I did a lot of research, and I COULD BE WRONG but I thought compressor surge was while you are under boost, not after you have dumped your air....I thought comp. surge was a constant and fast thudding sound, like a fan would make, the sound i'm getting is after I have closed the throttle, and the sound isn't constant, I mean it's like a bov sound...it winds down. Plus if it were stuck closed, where would all the pressure go?

 

I hope somebody sees this before I leave for my trip in 2 days :/ to ease my worries