Opel Astra G starting failure

First of all I apologize because I do not know where I must introduce myself.
I have studied electromecanica and one day I would like to set up a small workshop, although I know that I have a lot to work.

I have the problem that when trying to start the engine it takes to start and then the revolutions are seen to play between the 850 rpm at least until it stabilizes or stops

.

I would appreciate your help to solve it because it is my own car .

Greetings and thank you all.

Hi Piter112, welcome,
you should put more data for the identification of the car, for example if it is diesel or gasoline, displacement or engine type.
So you comment your car is gasoline? The instability of the idle can be simple dirt in the admission butterfly box, faint and clean it well of any dirt that it has and test if it goes better.
The theme of butter is usually moisture, which is condensed at the top of the engine, can be due to poor oil quality, due to compression leaks to the crankcase, because some water passes to the oil, etc. ..
I hope it helps you, greetings and encouragement and encouragement

Verify whether when there is white smoke, it may be that you have a damn cuisine or head packaging.

To start you must tell us about the car, we speak, second the emulcion in the lid is never normal, but it can be not so record, the delay of the starting you mean until the engine is put into operation or that the starter engine takes time to turn?

The model is Opel Astra G 1.6 Gasoline Z16se Motor Code.
-I change the crankshaft sensor and remain the same, the start is not normal because it takes a bit and I must step on the accelerator a little, in cold sometimes it usually starts well due to the module detects the low temperature of the block and increases the slowdown, hot when the engine is at its temperature, it starts well (I suppose that by the temperature in the cylinders).

The delay is until the engine is put into operation and once the slowdown is stabilized in RPM

-the cream problem has a long time ago changes oil twice (disappeared). Sometimes filling a little because this series of models consume oil, but fill with its corresponding multigrade and the same brand
(Repsol Multimarca Sae 10W40) "my teachers told me that could be decomposition of the oil" that decomposition is possible for the same oil but of another carafe-it does not consume antifreeze although when I remove the cap fall drops of condensate.

-What oil you advise me.

As always a health and thank you very much for everything.