Citroen C4 2009 with THP engine - rough idle on starting

[lancia58]

Hi,

I have a Citroen C4 make year 2009. When starting the engine at the morning the idle is a bit rough and there is a light smell of fuel at the exhaust. After a five to ten minutes the engine rans smooth and there is no smell of fuel .
Any Idea what can be the cause for this

Thanks
Zohar

[wurlycorner]

It sounds like you may have a mis-fire. There are multiple possible causes of that tbh.
If it is a mis-fire then the first step would be to try and work out which cylinder the misfire is occurring on - do you have access to a scan tool that can fault codes and live data?
I'm not sure if the C4 has a misfire counter for individual cylinders or not - if it does, looking at stored fault codes and live data is the easiest way of identifying which cylinder.

If you don't have access to that, then take off the plastic cylinder head/cover and while the engine is running (and running rough) unplug and re-plug in each coil pack individually to see if there is a difference in how the engine runs - note this might cause an engine management fault light to come on, but don't worry about that.
When you unplug one, if it makes the engine run worse, that cylinder is not the faulty one.
If it makes no difference, that one is the faulty cylinder.

If it is a faulty cylinder, once you've identified which one, first try swapping the coil to an adjacent cylinder and re-test unplugging each of those - has the problem moved? If so then you have a faulty coil - replace that. If it hasn't moved, then take out the spark plug on the faulty cylinder and inspect it. Might be a faulty plug or if not, the condition of the plug will help identify what the cause might be.