Mystery Fault

[Mathi1]

Hi, I’m writing to you as a last resort. I bought a 10 reg DS3 Sport 6 weeks ago and it has developed a problem that no one seems able to identify or fix. I have had the car into 3 separate garages and it is still not fixed. It has cost me a fortune so far and I am left with a car that I may have to sell for scrap as NO-ONE seems able to fix it. I have considered placing the car into a Citreon dealership but in my part of the country there is a minimum of ‘THREE’ weeks wait just to have the car diagnosed?and all they will do is come up with the same fault? I have had the car diagnosed 3 times by 3 separate garages and each time it comes up with the same fault. (replace Lambda sensor) When this part was replace the fault still persists. I ended up having ALL the Lambda sensors replaced and the fault still persists? The issue I’m having is that the car runs fine, no warning lights appear but when it sits ‘idle’ it ‘revs’ and ‘shudders’, seems to be hunting for fuel or air? I have had Fuel pump replaced and other things done but the fault still exists. I cannot spend anymore money having it looked at and even if I could wait 3 weeks for Citreon to look at it they would just find the same fault in diagnostic? I always wanted a DS3 but this experience has ensured that not only will I ever buy a DS3 again but I will not ever buy a Citreon. Any last minute advice before I get shot of it would be appreciated, Thanks

[Chris_Blue]

Needs a walnut blasting
what error codes are coming up?

Also could be HPFP but seems you have already done that

[NZDS3]

what are the ShortTermFuelTrim readings while running?

If its adding 10-20% more fuel the is an air leak around the MassAirFlow meter. This could lead it to think the lambdas are reading wrong or unabld to correct mixture (experienced on different make)