The Pitstop

11:12 AM

@Zaid I've chucked a reply

probably just p#ssing into the wind

Zaid

@motosubatsu thanks. He's probably going to be upset though...

@Zaid yeah probably.. but that would be his problem

2 hours later…

1:36 PM

Howdy Peeps!

@Zaid - I'd suggest when you tell a poster something which looks like spam (in this case, MMO), ensure you tell the poster they should include their "affiliation, if any" to preclude such situations or it will look like spam. I think that's truly what you are getting at here anyway.

@Pᴀᴜʟsᴛᴇʀ2 to be fair that's basically what Zaid said

"If you are affiliated with the oil then you need to disclose it"

1 hour later…

Zaid

2:45 PM

Umm, yeah. I tried to avoid blanket accusations

I saw it. I think @Pᴀᴜʟsᴛᴇʀ2 missed it in the preceding comments.

@BobCross out of curiosity what symptoms are you seeing on the WRX?

3:43 PM

3/4 throttle boost oscillation with no boost leaks

same with full throttle but I don’t get to do that often

It looks a lot like a solenoid that can’t switch states fast enough and is defaulting to mechanical boost about once per second

yeah that sounds about right - what sort of max/min boost figures are you seeing>

Subaru WRX Boost problem. Leak or bad solenoid?

4:27 PM

Here’s a video example (not mine but very similar)

►

That’s a 2002-2003 because yellow needles on the gauges and the tach is in the wrong place.

when yours oscillates does it overboost?

or does it "bounce off" normal full boost?

Bounce. Very similar to what you see on that video.

Subaru 16102AA360 Solenoid Valve amazon.com/dp/B00IGZRQDU/ref=cm_sw_r_cp_api_i_5y0rCbT0CYC8Y

Weird. The normal SE app won’t let me paste anything. It’s not a phone problem.

I’ll try the 360 part number and report back

4:47 PM

yeah I've been doing some digging and it looks like that's the right one

You could augment your answer with 160 for 02 and 03 but 360 for 2004-07

if cleaning/replacing the BCS doesn't make it go away my next thought would be wastegate actuator rod (or more specifically the spring) - if that's getting worn it could be causing the wastergate to be opening at too low a boost pressure

you can adjust the preload on the spring to compensate but it's a laborious process of trial and error (apply small change.. drive.. apply small change... drive)

@BobCross yeah I've tidied it up a bit to make that clearer

5:06 PM

@motosubatsu - I surely did miss it. My apologies.

5:18 PM

Yeah I looked at the wastegate kind of sideways before hearing the BCS suggestion. When I saw a video of the exact same symptoms, I decide that replacing a 15 year old part probably wouldn’t make anything worse....

@Pᴀᴜʟsᴛᴇʀ2 no worries.. figured that was the case :)

@BobCross the BCS is still the most likely culprit (if you've ruled out any boost leaks)

also worth having a good look over the vacuum line going to it - sometimes they perish a bit around the restrictor pill

that can be just enough to throw the BCS operation off without showing up as a typical boost leak

my money is on the BCS though - they are basically central to the whole boost control process (mechanically speaking) and it doesn't take much wrong with them to wreak utter havoc!

Had one fail on my first Impreza - it was intermittently sticking causing the car to sometimes suddenly and completely cut boost at WOT, it was so jarring it felt as if you'd driven headlong into a brick wall!

2 hours later…

6:59 PM

I actually replaced all the vacuum lines connected to the wastegate not long ago

I was worried about the T and the associated lines. Turns out that was a good call but a different problem

7:51 PM

@motosubatsu - That NTSB article on MMO ... wow. Gotta love that. Though it sounded like they were using the MMO in excess of instructions. 1:100 ratio is not a lot. I guess if you have 200 gallons of fuel in the tank and drop in two gallons of MMO, that's quite a bit of MMO, but not that stout of a mixture. Things which make you go Hmmmmmm.

2 hours later…