Blue smoke from exhaust, don't think its oil?

Hi, I'm new here as I've just bought my first C3. I bought it as a non-runner (clutch) and have just gotten round to replacing it - It also had a reconditioned engine fitted by the previous owner as well as a new head, gasket and cambelt kit. Sadly, I have noticed an excessive amount of blue smoke coming out the exhaust. I don't believe it is oil though for a number of reasons, it smells like diesel rather than that sweet smell you get with oil, its only really noticeable at 2000+RPM and I have another turbo diesel car that DOES burn oil (5L of it a WEEK!) but the C3's smoke is much darker (probably darker than the label on a bottle of Pepsi), much less of it and it dissipates much more quickly.

I have read on a number of other websites that blue smoke can mean there's a problem with the fuel system as well. Faulty injectors can cause oil and diesel to mix or cause diesel to seep down the bores and into the sump, dilating the oil enabling it to leak past the rings. I've also read that an incomplete combustion or even air in the diesel can cause blue smoke too! Hopefully the information below will be of help to someone who might be able to give an educated guess as to what's wrong.

When revving the car whilst stationary, if you apply a bit of pressure on the accelerator and gradually rev it up there is very little smoke. If you were at idle and just planted the accelerator on the floor, quite a big puff of it comes out. When taking your foot off the accelerator, the revs die down but the car seems to dip below idle and starts spluttering as if its going to stall out for 1-2 seconds before revving itself back up to idle speed. This happens every time you rev it which is making me believe it is probably down to a fuel problem. If you were to drive it and rev it to maybe 3.5K RPM and then put the clutch in, blue smoke still comes out for 10-15 seconds where as this doesn't happen in idle no matter how hard you rev it or for how long.

Hi DP1990

If you don't think its oil, then its going to be diesel.

The injectors you have can easily be damaged if the fuel filter is neglected. I would say the injectors, or an injector is at fault for my first guess.

They are expensive to replace and would easily make a car uneconomical to repair and a good reason to move it on.

If you wanted to get an idea of the condition of the injectors, do a quick leak off test.

how to perform a leak off test on a C3 diesel 16v.

Alternatively a fuller diagnostics can be performed by an online delphi injector testing service (ebay).