My ST has lost boost and I can't find the cause

[RCode]

I know there are a bunch of threads on this, but I am genuinely perplexed on what my issue is. Yesterday I lost boost pressure suddenly while out on a drive. No CEL.

Normally this is due to my charge pipes popping off, but upon inspection they are all on tight. I'm using Whoosh's silicone pipes and they have held since installing them a few years ago, even after several track days.

Next up was to check the wastegate, my dad says the actuator arm isn't moving when revving. We replaced the solenoid, however we get the same result. I checked the AP and I'm honestly not 100% sure what these gauges are telling me, but I turned on the status and WGDC Actual, I do see movement on the WGDC gauge:




The only thing I haven't been able to check so far is the bov due to time, but if the wastegate arm isn't moving at all, could that even be the cause? I'm not sure what else I'm missing, I would think a sensor would cause a CEL. There was no pop or noise before it lost boost. I had it at one moment, went to pass a car and had no power. I'm on a Stratified tune with no eco slot so I didn't switch slots, and also running a Whoosh intercooler. I have a quick video if it helps.

https://youtube.com/shorts/JGk4OzQtPO0

I would greatly appreciate any help!

 

[FiestaSTdude]

Maybe remove the little plastic elbow on the passenger side of the turbo and feel the turbo to make sure it’s spinning and doesn’t have too much play. I’d definitely check the bov as well.

 

[RCode]

Maybe remove the little plastic elbow on the passenger side of the turbo and feel the turbo to make sure it’s spinning and doesn’t have too much play. I’d definitely check the bov as well.

Ya I'll definitely give it a shot, I didn't have a lot of room to work underneath the car today to check the turbo. I just imagined with the bypass valve I might hear kind of a whoosh noise if it's stuck open?

 

[dhminer]

Can you hear the turbo spooling under load?

 

[akiraproject24]

Looking at your boost gauge, it looks to be trying to build boost (you went from -11 vacuum to -.67. If you havent messed with your bypass valve diverter yet I would). If that were stuck, your options are much nicer than if your compressor wheel wasnt spinning right. I wouldnt replace it outright though without checking what the guys below are saying to check

dhminer and FiestaSTdude are sniffing at something that would suck big time.

 

[RCode]

Can you hear the turbo spooling under load?

It's honestly hard for me to tell, I think I'm hearing it spool up, but my ears could be tricking me. There is definitely no wastegate opening and closing. Otherwise nothing alarming sound wise. No smoke that my parents saw who happened to be behind me. I would think if the compressor went out I would have heard or saw something?

Looking at your boost gauge, it looks to be trying to build boost (you went from -11 vacuum to -.67. If you havent messed with your bypass valve diverter yet I would). If that were stuck, your options are much nicer than if your compressor wheel wasnt spinning right. I wouldnt replace it outright though without checking what the guys below are saying to check

dhminer and FiestaSTdude are sniffing at something that would suck big time.

I will check it next. I would be kind of surprised if I blew the turbo at 39K and a simple 93 tune, but we'll see.

Is it at all possible it's the actuator itself? I don't see those failing these cars but my Dad thinks it could be.

 

[dhminer]

It's honestly hard for me to tell, I think I'm hearing it spool up, but my ears could be tricking me. There is definitely no wastegate opening and closing. Otherwise nothing alarming sound wise. No smoke that my parents saw who happened to be behind me. I would think if the compressor went out I would have heard or saw something?




I will check it next. I would be kind of surprised if I blew the turbo at 39K and a simple 93 tune, but we'll see.

Is it at all possible it's the actuator itself? I don't see those failing these cars but my Dad thinks it could be.

It’s possible it’s the actuator. Do you have an air compressor? If so, you can test the wastegate. Disconnect vacuum line that runs from wastegate to boost control solenoid, disconnecting it from the solenoid. Then push 7-10 psi into the wastegate and see what happens. I’d be surprised if it was the wastegate, but nothing is impossible. I would venture that akira is correct that is the BPV.

 

[RCode]

It’s possible it’s the actuator. Do you have an air compressor? If so, you can test the wastegate. Disconnect vacuum line that runs from wastegate to boost control solenoid, disconnecting it from the solenoid. Then push 7-10 psi into the wastegate and see what happens. I’d be surprised if it was the wastegate, but nothing is impossible. I would venture that akira is correct that is the BPV.

Well, I have a starting point, I appreciate all the responses so far. I'll check the compressor, then bpv, then the wastegate assuming the latter leads nowhere. With the BPV, I think it starts open, then closes as throttle is applied right? So is there an easy way to tell it's not closing? I wasn't sure if there might be a way to manually check.

 

[RCode]

So the bypass valve was stuck when pushing from a certain angle and very sticky, replaced it, confirmed that the compressor is spinning and looks fine. No play in it. But still no boost! I'm at a loss, this is so weird. I'm not hearing the bpv make any noise or the compressor spin. So I would think the wastegate isn't the issue?

I switched tunes as well to see if I maybe accidentally switched slots but nothing. Engine runs fine, no rough idle. I'm completely stuck here. So weird.

Is there maybe a sensor that could be an issue? I don't have any codes though. So I doubt it's that or the ecu.

Ok quick update, we're pushing 7-10psi into the wastegate and it isn't opening, no movement whatsoever. So maybe try a new wastegate?

 

[Mega ST]

Seems if the WG wasn't opening you would overboost so maybe stuck open? Did you check the WG flapper on the turbo? Can you do a boost leak test from turbo outlet? Helps if you have an air compressor. I use a PCV cap with a valve stem attached to the top and use an air regulator to regulate pressure. It would have to be a bad leak to cause 0 boost tho.

 

[RCode]

Seems if the WG wasn't opening you would overboost so maybe stuck open? Did you check the WG flapper on the turbo?

We disconnected the WG actuator from the flapper, and the flapper moves freely. But when revving the engine and pushing that psi using an vacuum guage it doesn't move. At idle does the wastegate stay open? Because I agree, it sounds like it's not closing, causing a leak and not letting the turbine spin to build boost.

Unless the handheld vacuum Guage just isn't enough, but it is getting to 7-10 psi

Edit: We actually might be using the wrong gauge, it might not be pushing pressure but creating a vacuum instead. That was a dumb mistake. Back to Harbor Freight

 

[RCode]

We disconnected the WG actuator from the flapper, and the flapper moves freely. But when revving the engine and pushing that psi using an vacuum guage it doesn't move. At idle does the wastegate stay open? Because I agree, it sounds like it's not closing, causing a leak and not letting the turbine spin to build boost.

Unless the handheld vacuum Guage just isn't enough, but it is getting to 7-10 psi

Edit: We actually might be using the wrong gauge, it might not be pushing pressure but creating a vacuum instead. That was a dumb mistake. Back to Harbor Freight

Well shoot, the WG works with the proper pressure gauge. Going to try a boost leak test next, but I'm not hearing any whistling or sounds that indicates air is leaking, I wouldn't expect a small leak to suddenly go from full boost to no boost at all. I would just expect a drop. Plus I don't hear the turbo spooling at all. But the compressor is intact.

 

[dhminer]

Well shoot, the WG works with the proper pressure gauge. Going to try a boost leak test next, but I'm not hearing any whistling or sounds that indicates air is leaking, I wouldn't expect a small leak to suddenly go from full boost to no boost at all. I would just expect a drop. Plus I don't hear the turbo spooling at all. But the compressor is intact.

Really got me scratching my head. It’s building some amount of boost otherwise the boost gauge would always show vacuum, I think. If it’s a boost leak it’d have to be quite large. What happens if you just disconnect the vacuum line from the wastegate so it’s always closed? Will it boost then?

 

[RCode]

Really got me scratching my head. It’s building some amount of boost otherwise the boost gauge would always show vacuum, I think. If it’s a boost leak it’d have to be quite large. What happens if you just disconnect the vacuum line from the wastegate so it’s always closed? Will it boost then?

I tried that exact thing yesterday, but no boost! I checked to see if air was even entering the solenoid, but there was no pressure to push it open, which is really weird. The compressor isn't moving at all under idle or revving, so I've just come to the conclusion that my turbine probably deconstructed itself. I'm going to try and confirm this week by taking off the downpipe and looking at it, before ordering a new one.

I just would have thought I would have heard that happen, or seen some other kind of sign. But the other (very few) failures I've seen on stock turbos show the blades off of the shaft, so I'm guessing the entire shaft is still intact, but with no (or few) blades, there's nothing to spin the compressor and build boost. This also explains why I lost boost instantly.

So that sucks, but I can't complain too much. Tuned, plenty of track days, lots of spirited driving. Just funny it happened on a casual drive on a super hot day. I'm gonna start working on finding the best place to source a new turbo.

 

[Mega ST]

Are you running a cat? Possibly clogged? I've had turbines com apart on some Garret stuff, they don't usually fail out of the blue unless struck by debris. I had one throw a blade that went thru the turbine housing but I was pushing 40psi PSI on a 2.0l.

 

[RCode]

Are you running a cat? Possibly clogged? I've had turbines com apart on some Garret stuff, they don't usually fail out of the blue unless struck by debris. I had one throw a blade that went thru the turbine housing but I was pushing 45psi PSI on a 2.0l.

I am running a cat. Is it easy to tell if it's clogged?

 

[Mega ST]

Drop the mid pipe and take a look. Also cat material around the tail pipe or change in exhaust tone. Does the engine free rev normally?

 

[RCode]

Drop the mid pipe and take a look. Also cat material around the tail pipe or change in exhaust tone. Does the engine free rev normally?

The engine free revs ok, maybe it's a little more lethargic? I feel it more under acceleration, light pedal input doesn't feel any different, but add more throttle and the engine doesn't pull hard. I didn't see any cat material around the exhaust. Maybe the engine sounds deeper?

Either way, worth taking a quick look at this point. But would a clogged cat not allow the turbine to spin at all?

 

[haste]

Clogged cat would pretty much choke off the engine(diesel world anyway). I would think some nasty smokeage would be coming from the outlet of your exhaust if you had a catastrophic turbine failure.

 

[Mega ST]

It can def impede spool. But I think it’s a long shot. Process of elimination….