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Discussion Starter · #1 ·
Hi all,
I own a 2016 Ford Focus ST(a shocker I know) and for the past 3 months I have been chasing this boost issue. I just got a job again so I have money to actually start fixing it instead of just doing the monthly payments. The car is only boosting half of what it usually does and it reads out a check engine code of P0299 (Turbocharger Underboost). This issue occurred while I was WOT and dogging on it, when I went back to my boyfriends house I popped the hood and the intake box had fallen apart I then proceeded to piece it back together. I brought it to a dealership where they told me the issue is being caused by a faulty air inlet, I just dont feel like that could be the issue it is such a small piece, but nonetheless the air inlet doesn't fit around the tubing flush and doesnt seem to actually close up enough to be "air tight", if this can be the issue and im stupid please let me know, I want boost back. Heres a list of things I have replaced,
-Wastegate Actuator Sensor
-The wastegate itself(I also adjusted the preload correctly)
-The air intake
-The air intake box itself
One side note is that I currently have the bumper off for ****s and giggles, there couldnt be a possible way that this is throwing like some limp mode at me right? I'm off to drink my sorrows away!
 

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Discussion Starter · #3 ·
Did you check the bpv
I did not, I am new to Turbocharged cars(I owned a 97' Integra GS and a 2011 E92 328i) so what should I be looking for in a faulty BPV, and should I look into getting a BOV instead I know it doesn't add performance but I heard that in some cases it can decrease power. Sorry for my forced induction ineptness! I can always take pictures for you tomorrow. Also thank you for your help.
 

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2016 ST2, Shadow Black, E30, MonsterFMIC, GFB DVX+ BPV, ALEX' ShiftBushings, PCV-OCC, Innovative RMM
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How did you adjust the preload "correctly"?

The BPV or symposer diaphragms can crack and leak.

If you don't want more psssh noises, a BPV wont require clearing and oiling more like a BOV in the stock location.

If you get aftermarket BPV, the bracket goes on top. Read the directions if you get one too, as some want a manifold vacuum source but others work best off the stock solenoid.
 

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Discussion Starter · #5 ·
How did you adjust the preload "correctly"?

The BPV or symposer diaphragms can crack and leak.

If you don't want more psssh noises, a BPV wont require clearing and oiling more like a BOV in the stock location.

If you get aftermarket BPV, the bracket goes on top. Read the directions if you get one too, as some want a manifold vacuum source but others work best off the stock solenoid.
To my knowledge of how the wastegate works it opens a valve that lets air in and builds pressure. So if the preload is set too “high” you won’t make enough boost, if it’s set too “low” you make too much boost too early and can throw an over boost code. I bought a Turbosmart Wastegate I can take pictures of it installed and show you what I mean.
 

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Mods? Miles? Codes?
 

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2014 ST3. Garrett GTX2860R Gen 2. FBO
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To my knowledge of how the wastegate works it opens a valve that lets air in and builds pressure. So if the preload is set too “high” you won’t make enough boost, if it’s set too “low” you make too much boost too early and can throw an over boost code. I bought a Turbosmart Wastegate I can take pictures of it installed and show you what I mean.
What metered air source did you use to adjust preload? Tell us exactly how you came to your end adjustment. This is crucial.
 

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Discussion Starter · #9 ·
What metered air source did you use to adjust preload? Tell us exactly how you came to your end adjustment. This is crucial.
I used an air compressor set to 7 PSI, I had an extra hose I connected the wastegate then to the compressor. I set the valve all the way closed then put the nuts between the valves, I then would keep opening the valve and moving the nuts forward until the valve could completely open.
 

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2018 Ford Focus ST1 with a 2867 gen 2
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FWIW, my wastegate flapper bushing was absolutely shot at just a touch over 50K miles, so with yours at 78K, I imagine yours is shot, too. My commute was pretty easy on it and I rarely was into boost much on the way back and forth to work, so with it failing at that kind of mileage, it may be worth checking. With the bushing allowing the flapper valve to not seat flush on the opening, it wasn't holding boost like it should have even with a WGDC at 100%. Depending on how much yours is worn out, it could be causing problems.

Just an idea, but you COULD look at upgrading.... An AP, intercooler, and 3" downpipe are really all you NEED for a big turbo install, and it's way more fun than the tiny stocker.
 

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Discussion Starter · #11 ·
FWIW, my wastegate flapper bushing was absolutely shot at just a touch over 50K miles, so with yours at 78K, I imagine yours is shot, too. My commute was pretty easy on it and I rarely was into boost much on the way back and forth to work, so with it failing at that kind of mileage, it may be worth checking. With the bushing allowing the flapper valve to not seat flush on the opening, it wasn't holding boost like it should have even with a WGDC at 100%. Depending on how much yours is worn out, it could be causing problems.

Just an idea, but you COULD look at upgrading.... An AP, intercooler, and 3" downpipe are really all you NEED for a big turbo install, and it's way more fun than the tiny stocker.
hey rob I would love to get an AP, but I’ve sunk $800 into this car and it still isn’t making the boost it should. I just got paid today so I can sink a few hundred more dollars into this issue.
I’ll check the flapper bushing valve
 

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2018 Ford Focus ST1 with a 2867 gen 2
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Maybe someday then on the AP. :)

If it's the bushing then you may want to get ahold of @SSgtjrobertson as I think he had some info on replacement kits for the bushing. The alternative is to replace the entire turbo...
 

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2014 ST3. Garrett GTX2860R Gen 2. FBO
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I used an air compressor set to 7 PSI, I had an extra hose I connected the wastegate then to the compressor. I set the valve all the way closed then put the nuts between the valves, I then would keep opening the valve and moving the nuts forward until the valve could completely open.
So you got it partway correct. You are setting crack pressure (which means the pressure the canister JUST begins to move the wastegate flapper arm), not full open pressure.

With nothing hooked to the turbosmart wastegate canister, snug the nuts against the wastgate flapper arm so that there is 1 or 2 turns of threads pulling the flapper arm closed.

What spring do you have in the turbosmart canister? 7psi I'm assuming? So Set your regulator to 7psi.(For anyone else reading. If you have a stock canister this will be 5psi)


Hook the air source up and watch for movement of the arm. It will be very very small.

If you hook the metered air up and no movement has occurred, loosen preload some, small increments.

If you hook it up and lot of movement occurs quickly, tighten preload up.

Again, you are setting the pressure at which the valve just begins to open. Not where it's fully opened.


I prefer to use a mityvac hand pump because it's more precise.
 

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2018 Ford Focus ST1 with a 2867 gen 2
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Good luck. Hope it's something minor and doesn't cost much to fix
 

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Discussion Starter · #17 ·
Hey updating again, I’ve called all dealerships and they are all 1-2 months out except for the original dealership I went to. I want to check the bypass valve when I get home, I wasn’t sure how to tell if it was broken/sticking or binding.
 

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2018 Ford Focus ST1 with a 2867 gen 2
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It's pretty easy to just remove the unit. Jack up the passenger front side of the car and pull the wheel. You'll need a 5mm hex wrench to get back in there, though, and you MAY want to just get a 5mm socket so you can use an extension to get back in there. I think I used a ball head 5mm wrench, but I had to turn it with a wrench to get the bolts broken loose. They were pretty snug.

You may find that your factory bypass valve is torn or the o-ring is shot. In either case, you will either need need another factory unit (don't bother since it'll just tear again) or a Mountune BPV if you want to stick with a bypass valve. Uprated Air Recirculation Valve 2226-Trv-Aa - Ford Focus Power & Performance Upgrade (mountuneusa.com) I ran one of those for a while before I got the Tial BOV. If you want to go with a blow off valve instead of the recirculating valve, you'll need a Turbosmart Block off plate (Ford Focus ST Blow Off Valve Block Off Plate by Turbosmart (awdmods.com) plus a blow off valve of your choice, a mount for it (I just used a cheap T I put in the factory hot side), and a way to actuate it (MAP tap, for instance).
 
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