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Focus Mk4 / Ecoboost 1.0 Turbo Underboost Fault


Dark Andy
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Hi, driving home through France yesterday, my Mk4 Focus cut power and displayed the "orange spanner" fault error while climbing a hill with cruise control active. After pulling over at the next rest area and switching the ignition off and on again after a few minutes, the fault light went out. Between turning the ignition off and on, I read the fault codes on my phone and found a "Turbocharger underboost" fault which then cleared itself. I continued my journey (another 400+ miles) with no further issues.

Do you think this is a one-off glitch (possibly a combination of low revs, steep hill, car loaded with people and cases, and French petrol) or something more sinister that's likely to occur again?

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Hi Andy, 

I've been using French petrol (E10 and E5) for over 15.000 km without any issues so I would rule it out.

What does low revs mean acutally? Below 2000? Below 2500?

Besides the DTC were you able to get some freeze frame data? 

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Hi, check the vacuum hoses that connect to the turbo control unit. A small split or crack in one of these hoses can cause underboost fault 

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On 6/5/2024 at 12:45 PM, RaduF86 said:

Hi Andy, 

I've been using French petrol (E10 and E5) for over 15.000 km without any issues so I would rule it out.

What does low revs mean acutally? Below 2000? Below 2500?

Besides the DTC were you able to get some freeze frame data? 

It's just done it again, so I'll have a look and grab any data before I clear it.

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5 hours ago, granville_focus said:

Hi, check the vacuum hoses that connect to the turbo control unit. A small split or crack in one of these hoses can cause underboost fault 

Thanks - where should I be looking for those (2019 1.0l ecoboost, non-hybrid)? Had a quick, general look around under the bonnet but couldn't see anything that looked obviously broken/cracked.

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21 minutes ago, Dark Andy said:

It's just done it again, so I'll have a look and grab any data before I clear it.

Just connected my phone up but unfortunately the DTC has already cleared itself and there's no sign of anything (pending, etc) left behind.

As for details of when it happens, again similar situation - engine under load climbing a hill at around 1,250 - 1,500 rpm, just at the point where I'd normally change down a gear.

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52 minutes ago, Dark Andy said:

Thanks - where should I be looking for those (2019 1.0l ecoboost, non-hybrid)? Had a quick, general look around under the bonnet but couldn't see anything that looked obviously broken/cracked.

On the Mk4 chain engine there's a vac solenoid mounted horizontally on the front right of the engine.  Has a little top hat at one end with three small vac pipes.  I think that'll be the boost solenoid but will have another look if not.

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2 hours ago, TomsFocus said:

On the Mk4 chain engine there's a vac solenoid mounted horizontally on the front right of the engine.  Has a little top hat at one end with three small vac pipes.  I think that'll be the boost solenoid but will have another look if not.

This? All looks OK - no cracks or splits. The only thing I could find is that there is some play where one of the hoses connects to the air intake.

20240609_202721.jpg

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13 hours ago, Dark Andy said:

This? All looks OK - no cracks or splits. The only thing I could find is that there is some play where one of the hoses connects to the air intake.

20240609_202721.jpg

Yes, that's the one.  Those pipes all look in good condition as you say.  As they're under vacuum, a bit of play with the engine off isn't an issue as it'll get sucked together with the engine running, though you could use a cable tie to make sure the loose pipe connection is fully sealed.

Unfortunately I haven't been able to confirm which vac line goes the turbo actuator.  The turbo is on the back of the chain driven 1.0 so can't be seen from a bonnet picture and public parts catalogues don't go beyond 2016.  Usually I check 'complete engines' on eBay to confirm things like this, but none of them have the turbo still attached unfortunately.

If you can find the turbo actuator (small metal drum on the back right of the engine with a single vac line coming from it) then you can trace that line around to the front, and hopefully the actuator in the picture, although there are a lot of vac lines on this engine for some reason.  I would need to see the full engine from various angles to work out where they all go.

Back to your original fault, the most likely cause is a loose boost hose somewhere between the turbo, intercooler and intake manifold.  Second is the boost actuator or pipework as discussed above.  And third would be the turbo itself, the wastegate on these isn't the most robust and could be leaking some boost when 'closed'.

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17 hours ago, Dark Andy said:

As for details of when it happens, again similar situation - engine under load climbing a hill at around 1,250 - 1,500 rpm, just at the point where I'd normally change down a gear.

I believe I am in over my head here. I thought the turbo can't provide much boost below 1700 rpm. Is the turbo even spinning below 1500 rpm?

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2 hours ago, RaduF86 said:

I believe I am in over my head here. I thought the turbo can't provide much boost below 1700 rpm. Is the turbo even spinning below 1500 rpm?

The benefit of fitting a tiny turbo with modern manufacturing precision is virtually no turbo lag.  I reckon you'll start to see boost from around 1250rpm on this engine.

You can try watching the MAP sensor figures on your own engine through Forscan to confirm.

Although as it's an MHEV it might be slightly different to the OP's car.  The MHEV generator provides extra torque low down which allows a larger turbo to be fitted for more top end (particularly useful on the 155/170ps versions), as there's no longer the compromise on low end that a fixed turbo alone creates.

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On 6/1/2024 at 11:44 AM, Dark Andy said:

I continued my journey (another 400+ miles) with no further issues.

Do you think this is a one-off glitch (possibly a combination of low revs, steep hill, car loaded with people and cases, and French petrol) or something more sinister that's likely to occur again?

It's interesting to me that at no point have you said that the car/engine isn't running well or is not as powerful as it used to be. 

Perhaps there isn't a fault with the turbo/vac solenoid/piping etc. at all, maybe just a sensor issue triggering the management light that doesn't affect power delivery.

I don't have the chain driven 1.0 ecoboost but what I do know is that my engine would not like running at the low revs you mention, especially in higher gears and heavily laden.

Is your car an automatic? 

 

Ref. the turbo operation, on my engine the rotor spins even at tickover. The actual boost when driving is not linear just based on engine revs and is heavily dependent on the signal the turbo solenoid is receiving - gear selection, road speed, throttle position via the ECU.

(A photo of the turbo rotor parts attached for interest).

 

IMG_20240611_125809132[1].jpg

Edited by RayC333
Photo of rotor parts added
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11 hours ago, RayC333 said:

It's interesting to me that at no point have you said that the car/engine isn't running well or is not as powerful as it used to be. 

Perhaps there isn't a fault with the turbo/vac solenoid/piping etc. at all, maybe just a sensor issue triggering the management light that doesn't affect power delivery.

I don't have the chain driven 1.0 ecoboost but what I do know is that my engine would not like running at the low revs you mention, especially in higher gears and heavily laden.

Is your car an automatic? 

 

Ref. the turbo operation, on my engine the rotor spins even at tickover. The actual boost when driving is not linear just based on engine revs and is heavily dependent on the signal the turbo solenoid is receiving - gear selection, road speed, throttle position via the ECU.

(A photo of the turbo rotor parts attached for interest).

 

IMG_20240611_125809132[1].jpg

The power only reduced after the light came on and returned as soon as it was reset, in other words, it was as though the ECU (or whatever management system it is) turned off the turbo and then switched it back on with the restart. I also know what you mean about the revs being too low - to be honest it was just at the point where I would change down a gear - even though the engine is at no risk of stalling, it's just beginning to fall outside its useful power band

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Dark Andy, having the same problem (MK4 1.0 ecoboost b7da). Have you found any solution?

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Just a suggestion. If you don't have Forscan equipment you could invest in a very cheap ELM OBD scanner (eBay has lots of them).

With one of those and free app like Torque Light you would be able to see the actual boost pressure being made in real time on a smartphone (preferably with an assistant looking at the values).

Before I invested in Forscan I found the above set up very useful in diagnosing what was wrong.

For instance it would help to know if there is a general deterioration in boost or whether (as you currently believe) a sudden drop off.

On the earlier 1.0 Ecoboost a common turbo problem was down to failing silicone diaphragms in the vacuum pump.

I believe the later pumps have a slightly different design but may be an easy check to do. Shouldn't be happening in a car of your age but I wouldn't rule it out 

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3 minutes ago, RayC333 said:

Just a suggestion. If you don't have Forscan equipment you could invest in a very cheap ELM OBD scanner (eBay has lots of them).

With one of those and free app like Torque Light you would be able to see the actual boost pressure being made in real time on a smartphone (preferably with an assistant looking at the values).

Before I invested in Forscan I found the above set up very useful in diagnosing what was wrong.

For instance it would help to know if there is a general deterioration in boost or whether (as you currently believe) a sudden drop off.

On the earlier 1.0 Ecoboost a common turbo problem was down to failing silicone diaphragms in the vacuum pump.

I believe the later pumps have a slightly different design but may be an easy check to do. Shouldn't be happening in a car of your age but I wouldn't rule it out 

p0299 error code. vacuum pump valve have a different design diaphragm

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36 minutes ago, Vitaliy said:

I have found the solution )

You're missing a cylinder?😝

 

Sorry couldn't help myself😂

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4 hours ago, Vitaliy said:

I have found the solution )

Well, let us all know what the problem was, in case this crops up again!

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westgate bracet was broken, ia had no time to repair it, so ive manged to change it all)

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Managed to get a snapshot this time before it reset and deleted itself. Again, the same circumstances: under load, going up a steep hill (looks like I had more revs than I'd first thought)

20240624_173736.jpg

20240624_173655.jpg

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