C4 1.6 petrol turbo - power fluctuation / loss

[C4Turbo]

Has anyone encountered this or a similar problem?

Our C4 1.6 petrol turbo automatic hatch is 18 months old. In the past 6 months it has developed a sudden power loss issue, as though the turbo has cut out. it then appears to run in "safe" mode. It can last from 30 minutes to days. The worst example lasted over 500 kilometres on a long interstate journey, where it climbed a small mountain range in 2nd gear @ 20k/hr. (Citroen has no emergency service outside major cities). It is accompanied by rough idling and the somewhat hair-raising habit of not responding immediately to the throttle when, for example, entering traffic. (At all times, not just during power-loss). Power returns over a period of 15 to 30 minutes, gradually improving during that time. There is no apparent trigger for the power to return, for example when it is hot, cold, re-started, the next morning etc. Just when it feels inclined.

The car has been in the garage for 2 months and the dealer can not isolate the problem. To date they have de-coked the valves / head (that was apparently heavily coated) and checked the timing, though apparently the correct timing tools are not available in Australia, so they are currently hopping from France. (on a slow boat - hopefully not to China). Citroen refuses to look at Airflow, oxygen, Co2 or MAP sensors because there is no fault being registered in the fault logs. I personally feel, when all the evidence is assembled (coking engine, sudden changes in power, idling, throttle response etc., ), it will turn out to be a faulty sensor.

[Citroenmad]

It does sound like a possible sensor issue, as the turbo is no doubt being limited by the engine management cutting in and running on safe mode.

Its a shame your local Citroen dealer has not sourced the fault within the two months thay have had it.

I had the same kind of thing with a Seat Leon, it would be fine and then the turbo would be lost and the engine management light would come on. Really an iffy thing to drive with no Turbo. Luckily it was a loan car so I simply handed it back saying a light had appeared. Though that did turn out to be a sensor fault, how the dealer found that I don't know, as that particular one doesn't know an engine from a fog light.

When I have had problems with cars in the past, ones which were under warranty, and a problem which the dealer could not get a grasp of, I have had to take the car to independant specialists for them to diagnose and then I could report back to the main dealer for them to fix it.

[C4Turbo]

Good advice. Maybe a sophisticated dyno-tuner would pick it up.