Anyone come accross this unusual boost issue before ? Going up a hill in say 3rd, accelerator at a steady 2500 - 3,000 revs so not accelerating much just keeping it steady under load and the boost sounds like its almost pumping/surging and between pumps you get the DV releasing air. I've had it on ForScan and mapped the pressure and can see it pumping so it's definitely got a problem. If I drive slow and steady it's fine, if I floor it it's also fine with quick pull away etc.

I've changed the one way Vac valve first then the MAP sensor, now the MAF sensor and yesterday the  Charge Air intake Temperature Sensor and still does it. 

I've vaccume tested the turbo vac lines and the waste gate actuator is free and moving ok (I know these can get caught on the heat shield)

If you Google boost pumping/ surging I can see it's common across all models of ford with this engine fitted but no one seems to know what the cause is or more importantly the cure.

I have a turbo smart dual port valve fitted, full airtec induction system with turbo hard pipe and a Revo stage 1 map. Even switching back to std ford map for the car it still does it just not as loud as obviously not as much boost.

Anyone come across this before ? It's been doing it about a year now.

No issues with my (complete!y standard) 140 in the 5 years I had it.

Previous thread on this:

 

There's also a other thread I commented on a year ago but didn't get anywhere.

I have no loss of power or boost so not quite the same as that thread.

 

Loads of people have had it.

 

https://www.fordownersclub.com/forums/topic/147361-mk8-st-line-surging-issue/

 

https://www.fiestastforum.com/threads/surging-issue-when-in-boost.7027/

Lots on Reddit too but no one ever seems to reply with a fix or to say they fixed it and some are a few years old. Lots of suggestions though haha.

 

Still having this issue if anyone has any advice, ive now changed 3 sensors trying to diagnose it but still happening. I cant believe so many people have had the problem and no ones bothered to reply how/ if they managed to fix it. Youd think they just flogged the issue on to someone else 🙂

 

I don't have much of a clue so feel free to ignore.

If DV is dump valve, i.e non standard and no electronic control then there must be too much pressure leading to the air release.

What controls the turbo boost? - Wastegate or, more likely, variable vane (electronic control and feedback loop via vacuum triggered position sensor/actuator?
Therefore something is telling it to generate too much boost and that is what is causing the surging - the control system is trying but overboosting, releasing etc?
if DV fitted, can it be disconnected or other sensors disconnected and the effect on live data monitored.
Just random ramblings that may trigger something...

It's a fiesta so no fancy electronic controls I'm afraid, it's just a waste gate, actuated via a vaccume. 

There are sensors I can disconnect mainly MAF, IAT and Boost Pressure which are the 3 I've replaced, I've also replaced the one way vaccume valve and pipe. The only thing I haven't swapped out is the dump valve which I can do as I have a spare. 

It's weird because if it was producing overpressure/ over boost why does it work fine if I floor it ? It only does this if your acceleration is gentle but firm at around 3,000 revs and holding pedal steady.  Floor it and it's absolutely fine all the way to the gear change in every gear.

 

If you floor it then engine will accept any boost?
At constant throttle/mild acceleration, more boost than is necessary may build up but i don't know why  unless it's something that controls the wastegate.
If DV is actuating, there MUST be boost that exceeds its blow off pressure?
Does it make it worse or better if you disconnect the wastegate actuator?
Are there any wiring faults, can the voltages and sensor outputs be monitored and do they make sense?
Sorry I've now run out of ideas!

Yep driving it with a bit more passion is totally fine, it's just if your accelerating on say a long incline at around 2.5 or 3K revs and holding pedal steady it kind of surges. I'll try and get a video or Audio of it doing it I'm not sure if I've made one yet.

I can probably disable the turbo vaccume pipe but then won't there be no proper boost at all? 

I think I'd be tempted to swap the DV back to genuine ford one. Perhaps that's what's causing it. 

Back to "as built" sounds like a plan (although was there ever a Dump Valve as I thought they were not needed/never fitted by manufacturers?)  Sometimes, you just need to do something that CHANGES or even makes the fault worse that may (just may) get you on the right track?
The effect of no boost or full over boost at top and bottom of range is sometimes another useful thing just to see the effect (I'm still meandering )

I don't really do engines but I thought all turbo engines had a dump/ boost valve. This is the ford one it's cheap and nasty lol.

 

I thought a dump valve was the thing that makes the wooshing noise to release pressure (unnecessary?)
Turbo control is normally via wastegate which is internal to turbo (on the exhaust side?) or via variable vanes, again on the exhaust side so I am now confused on the part you show so I am probably past my sell by date!

You can buy both ( you get louder whoosh if it dumps to atmosphere though), turbo smart even do a 50/50 which diverts pressure to atmosphere and back into the turbo, or you can buy just an upgraded alloy and spring recirculating valve. 

All of them on the 1.0 fiesta are run from the vacuum pipe which also splits (and I've replaced already). 

10 hours ago, Shearers said:

I thought a dump valve was the thing that makes the wooshing noise to release pressure (unnecessary?)
Turbo control is normally via wastegate which is internal to turbo (on the exhaust side?) or via variable vanes, again on the exhaust side so I am now confused on the part you show so I am probably past my sell by date!

Petrol cars still all have wastegate turbos.  It's only diesels that have VNT.  The reason for this is that petrols already have a wide, progressive powerband.  Diesels only have a small powerband, so we can increase that with a VNT turbo.  Otherwise you're stuck with a small turbo that is really nippy around town but has no top end, or a large turbo that is great for motorway overtakes but too laggy to use around town.

The 'dump valve' on the EcoBoost is actually a recirculating valve and is not unnecessary.  These turbos spin up incredibly fast when the throttle is open, and when the throttle is suddenly released, the butterfly valve closes, but the turbo is still spinning at that point.  Where does all that compressed air go?  It backs up the inlet and causes compressor stall and over time would damage the turbo.  For this reason a bypass valve is added, this takes compressed air from after the turbo and dumps it back into the air intake piping before the turbo.  (Hence recirculating).  A dump valve is fitted in the same place for the same reason, but just dumps that air to the atmosphere, creating the noise.  Recirculating the air also has another benefit, it means there's less turbo lag in between gearchanges when the throttle is released.  (On old turbo cars the throttle had to be kept open during gearchanges to keep the boost up - fun fact, this is is how 'drifting' started in Japan, because they fitted turbos that are too big and needed to get round corners without releasing the throttle pedal each time.)

Have you got any fault codes from when you plugged in the diagnostic scanner?

Also, the dump valve you have needs to be adjusted. I would suggest looking at the instructions to see how that is done, as it's been over 7 years since I fitted my one and can't recall how to do that.

No fault codes I'm afraid and the turbosmart is adjusted perfectly as per instructions. I've even tried it soft as it goes and hard as it goes before resetting back to factory to see it an adjustment issue. 

What I need to do is eliminate it from the equation and stick the standard ford one back on but the weather at the moment is atrocious and I don't have a garage. Will update once I've done that.

On 11/22/2025 at 2:58 AM, Eric Bloodaxe said:

No issues with my (complete!y standard) 140 in the 5 years I had it.

Previous thread on this:

 You may be interested to know that after over a year, a “good” replacement turbo, vacuum pump replacement, boost solenoid replacement, fuel pump tappet replacement, dual port BOV removed and a block off plate installed in it’s place that it still does it

Driving me crazy! once i get off the ARK and it stops raining ill come back to this, if i have to ill take it to a Ford specialist to find out what it is, so many people have had the issue with this engine it needs resolving

4 hours ago, a7mag3ddon said:

Driving me crazy! once i get off the ARK and it stops raining ill come back to this, if i have to ill take it to a Ford specialist to find out what it is, so many people have had the issue with this engine it needs resolving

I’m thinking at this point it’s gotta be something electrical, I’ve checked for leaks pretty much everywhere there could possibly be a leak, I’m going to try and source ANOTHER boost solenoid this week and try that, be interested to see if you get anywhere with it

What part is electrical? Or do you mean a sensor? The turbo actuator is vaccume controlled, it could be solenoid but all this should be readable in live data to confirm.

Are you buying a genuine solenoid from ford?

10 hours ago, a7mag3ddon said:

What part is electrical? Or do you mean a sensor? The turbo actuator is vaccume controlled, it could be solenoid but all this should be readable in live data to confirm.

Are you buying a genuine solenoid from ford?

Can’t get the solenoids from Ford in Aus anymore but the one I bought was genuine used, either there’s a dodgy sensor somewhere that’s not reading properly, the solenoid isn’t behaving or there’s an issue with the actual signal to the solenoid

I’ve attached a photo of some data logging from a quick drive i did

10 hours ago, a7mag3ddon said:

What part is electrical? Or do you mean a sensor? The turbo actuator is vaccume controlled, it could be solenoid but all this should be readable in live data to confirm.

Are you buying a genuine solenoid from ford?

Is the centre part the bit where your getting the surging at constant revs ?

1 hour ago, a7mag3ddon said:

Is the centre part the bit where your getting the surging at constant revs ?

Yeah that’s flat to the floor, it’s not really surging so to speak, it’s really difficult to explain, it doesn’t go like it used to, and if I stick my foot in it, it kinda hiccups through the rev range like it’s losing power for 20ms or so, but every now and then if I give it the beans, it’ll go like it used to go with full boost and all, change gear and it’s gone, I’ll link a video of what the boost pressure does, might be useful idk

That video is with foot flat to the floor, straight off, then back to the floor, I’m not letting off slowly

https://youtube.com/shorts/Q5qSflkRMYE?si=M31arGXnsEKrJKZ2

My surge problem is not like that, if I boot it then no issues, mine is if going up at hill and hold the revs at 3,000 it will boost then blow, then boost then blow. I will try and get my phone under the bonnet and record the sound. Will take a look at your video now too.

Just watched, the problem I have and lots of others have is not the same as yours I'm afraid.