THP 155 Power Loss

[DS3_Quest]

Hey guys, been checking out the forum for a couple of years, but never had any input to give. Unfortunately it has now come to this point where my first post is for some advice.

I have a 2012 DS3 THP 155 Sport. The engine in this one is one of those that have all the problems unfortunately. I had the timing chain issue replaced under warranty 3 times for instance.
The latest problem was the #1 cylinder that decided to break a piston. After some research I realized that this is also a "common" problem on these "wonderful" motors.
I did not get this fixed at a Citroën dealer as the car was out of warranty when it broke. Everything seems fine now, well mechanically at least. The only problem I have now is that the car has no power.
It feels like it is supposed to up until about 2400rpm, after this it just kind of stays on the same power level. Foot flat makes literally no difference. I have not red lined the car or anything, as it does have new internals still making friends with each other.

Now I did a couple of checks myself. It does have boost all the way to the intake. I later also confirmed the Absolute Manifold Pressure seems nice and "boosty". There are no funny noises or any engine error codes.
I have to mention the car was also serviced at this dealer, so there might be an issue of the wrong spark plugs. Another funny thing is that the car is chipped. The chip adds a good 22 kW and about 50 NM torque, With the chip removed now there is literally no difference.
This is what I can not figure out. It is like there is (what feels like) a "blockage" or something that just won't let the engine do what it must.

The car is going to Citroën in two days to get a diagnostics check. Hopefully this will show me if the timing is not right or something like that.

Has anybody on here experienced a power loss like this before perhaps?

[BenS]

What mileage does your car have? Quite likely it is suffering carbon buildup on the injectors and valves. Drop Jamie from SP Tuning a message and he can book you in for a walnut blast to clean it up if that is the issue.

If that's not it, I am certain more technical gurus will have detailed suggestions Hope your car gets better!

[mjogreen]

I assume OP isn't from UK talking about kW.

[Chris_Blue]

ECU. Injectors, HPFP, Valves, fuel... take your pick

[trotters]

Is it intermittent or always slow? When mine did that it would sometimes come back alive (at least partly) after a long drive at high speed.

[Chris_Blue]

Is it intermittent or always slow? When mine did that it would sometimes come back alive (at least partly) after a long drive at high speed.

That would indicate inlet valves carbonned up, and a long hard drive drives up the heat to burn off the soot

[trotters]

I'm not convinced it was the inlet valves in this case. I had an induction terraclean and it didn't help at all. Using STP fuel system cleaner and driving down the motorway in 4th has so far solved it :snowy0:

[Dangerousfish]

I'm not convinced it was the inlet valves in this case. I had an induction terraclean and it didn't help at all. Using STP fuel system cleaner and driving down the motorway in 4th has so far solved it :snowy0:

Sounds like you've solved the issue yourself despite numerous suggestions otherwise. I've personally experienced the same issue as you which resulted in two engine replacements.

I wish I'd have know about adding a fuel additive and always driving mine in fourth, I could have saved a lot of money.

Out of interest have you seen the state of your valves first hand?

[trotters]

Nope, I haven't seen my valves. They could well be a mess, but I'm not going to worry about it unless the power drops again or I go for a remap

[DS3_Quest]

So the car went into Citroën for diagnostics but to no avail.. They want to spend a couple of days with the car to establish the cause of the problem.
After extensive research and reading I see that the power loss is another one of the many problems with these motors. It seems that most solutions were timing chain related.
This could be a factor here as it had to be refitted due to the piston replacement, however I do not believe it is to that extent on my car.
With some fiddling through various diagnostics the car decided to give me a static orange check engine light and static orange Service light.

An OBDII diagnsotics gave the following error codes:
P0033 - Compressor Discharge Electrovalve (Dump Valve) Control Fault Open Circuit.
P0238 - Manifold Entry Pressure Sensor Short Circuit to Positive Pressure too High.

This leads me to believe that it is a vacuum pipe that is not properly fitted. This is very likely as the guy who did the repairs is not a certified Citroën mechanic and he might have missed a pipe somewhere.
The last thing I have not checked is the Vacuum Boost Valve as I can not reach it without going deep underneath the car. The car is going on the lift on Thursday morning where I will investigate all the vacuum pipes behind the motor.
Now of course I am hopeful that it is only a vacuum pipe and not something bigger. I will post an update after Thursday.

Out of interest, Has anybody ever removed their circulation valve to see how much air comes out of the hole? Mine was sucking air into the hole with the valve removed.. This is curious..

[Dangerousfish]

Nope, I haven't seen my valves. They could well be a mess, but I'm not going to worry about it unless the power drops again or I go for a remap

Fair enough, it's your money

[DS3_Quest]

So I had the car in the lift this morning to try and find the problem. It would seem that it is the Air Flow sensor that is faulty. I did the standard multi meter test on it and the volts do not go up with the revs, it just stays static.
Has anybody ever monitored the MAF reading on these cars through OBD2? On all the OBD programs I run I do not get any Air Flow readings. I am not sure if this is due the OBD protocol on these cars or if it is because the sensor is faulty?

[Jamie@SPTuning]

Your not getting any logs for it as it doesn't have one(MAF).
EOBD fault description are also very generic but by p0033 I would assume that's referring to the DV on the turbo itself. If it's not opening on overrun it will give you excess high boost in off throttle situations hence the 2nd fault code you have.
Hope this helps...