2013 THP 155 engine stutter...any help guys?

[Saintsteve]

Firstly...sorry haven't been on here a while, all has been well .... Well almost.

Last year whilst under warranty, I complained about an engine hesitation whilst under boost, from 2000rpm to 4000rpm under load, and more apparent when I have more passengers on board or on an incline.(Most notable in 3rd,4th,5th,6th as the revs take longer to go from 2000 to 4000rpm.
The Citroen dealers agreed to clean out the inlet valves , and after their was done, it did help to cure the issue, but after just 8000 miles, it's returned and now the car is out of warranty and again after putting the car in for annual service , the dealership say they can't find this stutter , nor will it show any errors on diagnostic check. Getting ever so slightly hacked off as collected the car tonight from them, and stating i don't want the car back, I now have another 30 mile trip back to argue the toss.:mad:
Anyone have any suggestions as to what else could be wrong?
The car idles ok and has no issues above 4000rpm and performance is fine..

Do these engines suffer with the diverter valve diaphragm failing (boost pressure relief valve) bolted to the
Turbo?
Thanks all.

[Dangerousfish]

Main issues that seem to affect the THP are coking of the valves.

If you have a search through for "juddering", "stuttering", "engine failure" you'll find a bunch of issues related to the THP.

Any error codes logged on the ECU?

[Superfly Guy]

Possibly the HPFP maybe although on mine it went into limp mode and threw up an error code, it does sound like a valve cocked issue so maybe they didn't do too good a job the last time.

Did they show you a before and after shot of the valves as Jamie does (SP Tuning).

[Nomgle]

Do these engines suffer with the diverter valve diaphragm failing (boost pressure relief valve) bolted to the
Turbo?
Thanks all.

Yep - but when this happens, you'll effectively get a boost leak and the car will throw up a Low Boost fault code. If you're not seeing the orange warning light after a couple of hundred miles, this probably isn't your issue.
Mine looked like this when I took it off

[Saintsteve]

Just to update my post, once again the fault was traced to inlet valves being gunmed up.They have since used a machine to blast out the carbon deposists and now the car goes like a scolded cat, smooth and stutter free.
The only thing that worries me is that this has reoccured in just 8000 miles , and ive always run the car on 99 octane fuel with regular trips on the motorway and its come back so soon?.

Is there a PCV valve on these engines that may also be clogged and could also be worth looking at??

[Chris_Blue]

My inlet valves went at 19k miles, after using 98 RON and having a catch can fitted

PCV Set up had minor change when they went from the 150 to 155. Think Czar posted up photos
And PCV delete (Blanking off the PCV pipe) used to be a favoured mod in the old days....

[Superfly Guy]

And PCV delete (Blanking off the PCV pipe) used to be a favoured mod in the old days....

Before they realised it caused pressure issues.

[Saintsteve]

So where is the PCV valve located? Is it inside the rocker cover?

[Czar]

So where is the PCV valve located? Is it inside the rocker cover?

Here is the cam cover showing the various sections, and the PC valve flap diaphragm's.



Rear PC valve flap diaphragm in it's natural closed positions.


Rear PC valve flap diaphragm, open (this open position is vastly exaggerated, and will not be like this with it's lid on) showing the port passage exit.


Central sprung pressured diverter.


Diverter diaphragm (ignore the damage)


Underside of Diaphragm and pressure control spring.


Diaphragm direction/pressure control valley.


Central valley separation step


Right hand side, PC valve diaphragm flap, in it's natural closed position.


Valve diaphragm flap open, showing the port passage exit.


Firstly let me explain a little about the PCV, PCV is an acronym for Positive crankcase ventilation, inside the the cam cover there are a few entrapment passages and direction chambers, which do their best to separate the suspended oil particles from the passing vapour, this vapour is then vacuum drawn from the cam cover passageways through a valve flap, the first direction is through the rear PCV line into the intake manifold, next, when the vacuum draw from the turbo (building boost pressure) is greater than the vacuum draw of the induction stroke from the pistons, the rear PCV valve flap is closed, as is the diaphragm in the cam cover, this then changes the direction flow of the vapour, and the vapour is vacuum drawn through the passenger side PCV valve flap into the air intake flow pre-turbo, once off boost and steady throttle is resumed then the vapour is once again vacuum drawn through the rear PCV line.

Now the actual valve flaps themselves are merely free falling self closing rubber diaphragms, there is no spring or piston actuation on either valve flap, however there is a sprung chamber diaphragm, which opens/closes under the vacuum draw from both the inlet manifold and turbo vacuum draw, this dictates the flow direction, and in the later re-designed cam cover allows excess pressure to vent through the inbuilt pressure release sprung valve.

Hopefully this should help explain the PCV system, that said the very latest cam cover for the EP6 DT/S engine, has some slight revisions, to the oil mist guide and entrapment valley's, and the PC valve diaphragms are cylindrical free falling, as apposed to the oblong valve diaphragm flaps, in my images.

.....