ST-X 550 losing power

[Taylor]

Afternoon.

I took my 2014 ST-X 550 out for its first long drive since I got her less than a month ago, while I was driving I noticed she struggled to over take/get over 90.

I really put my foot down and the revs went high and then she lost all power and I had to pull over, the person behind me says she was spewing lots of black stuff.

I had RAC have a look and they can’t find anything wrong with her andshe doesn’t fault when they drive her.

I picked her up and then lost power on the way home so had her towed back to RAC and again they cannot find anything wrong still all I got was a problem with the turbo air intake sensor.
Has any had a problem similar to this? Without a check engine light coming on?

 

[landmannnn]

Are you saying there was a fault code present linked to the turbo intake sensor?

If so, that should be your first area to investigate.

 

[Taylor]

the people at RAC told me nothing was wrong with the turbo when I picked her up, before she broke down a second time.

 

[Pathfinder Benno]

Hey Taylor

I had a ongoing but intermittent loss of boost with my 550.
No check engine light initially.
Problem would self clear after shutting down.
I ruled out any mechanical problem with the turbo due always coming good.
My problem was due to an exhaust pressure sensor.
This was found after I actually had a check light & then finally checked for codes.
You need to get the ECM scanned & proceed from there.
It sounds like loss of boost pressure.
Turbo control is by electrical signal from ECM to a vacuum control solenoid. Electrical signal from ECM is a pulsed DC, more pulses more valve opening.
ECM determines boost requirement by looking at the following:
Crank position
Mass airflow
Accelerator position
Air intake temperature
Fuel rail pressure
Turbo boost pressure
Exhaust pressure
Exhaust temperature (#1)
If you can locate all these sensors, remove & clean connectors. Mas airflow sensor also includes air intake temperature sensor
Again, scan codes will point you in the right direction.
If I can advise any more

Benno

 

[Old.Tony]

There's two other possibilities here.

1) Turbocharger failure. These do wear (I'm on my 3rd turbo, but I tow a 2.5T caravan quite a bit so my wear issues are magnified). You can tell by removing the turbocharger's intake pipe (the plastic hose that connects to the front) and give the shaft a wiggle. If the shaft is loose, or rotates roughly, chances are the turbo's toast. As it spools up, the looseness in the bearings allows the shaft to wobble and the turbo stalls, dropping boost. Clouds of black smoke are the result, with no errors logged in the ECU - it is possible to notice this when monitoring the boost pressure and seeing it either not climb when expected, or begin to climb and fall away as the impeller stalls.

2) EGR valve fault. EGR is an emission control device, which routes some exhaust gas into the intake to dampen combustion. While it seems counter-intuitive to use a turbocharger to add more air and then add exhaust gas to take that air away, it does succeed in lowering combustion temperatures and reduce the production of nitrogen oxides (a result of higher temperature combustion). However, if the valve opens too much, combustion will still occur but won't be complete as there isn't enough oxygen available. This will result in large amounts of black smoke and no sign of errors in the ECU. EGR valve operation can be inhibited by simply blanking off the EGR tube itself (use a metal plate in place of the gasket, made from either 1mm stainless or 2mm mild steel). If the smoke problem has gone away, you have found the problem but may create another as the EGR flow sensor gets no input and the ECU realises you've been naughty, but at least you'll know it's the EGR valve that's an issue.