Vacuum inside crankcase.

[MillesimeEnjoyer]

Hello, i have a 92' BX 16.

I notice a high idle to about 1500-2000. This does happen often and is very annoying

The car also sometimes wont start when engine is warm, it seems as if its drowning itself (large cloud of black smoke when eventually started)

When i plug the hole to the oil fill cap from the air box, the idle returns to normal...

What should i do?

[panky]

I had exactly this on my GT. It turned out that the second choke on the Solex was sticking open very slightly sometimes, some penetrating oil, manipulation of the linkages and a final lubrication had it working as it should. The car had never been a good hot starter but now it's perfect.

[MillesimeEnjoyer]

Thank you Panky for the advice but i have a solex monopoint injection.
The problem also started when i replaced the head gasket.
Thanks in advance for the advice.

[xantia_v6]

I am not familiar with the particular injection system, but it is normal that there is a restriction or pressure valve in a hose between the crankcase and inlet manifold. Could this device have been damaged of omitted when the head gasket was replaced?

[Jaba]

We have never had monopoint injection cars here so are not familiar with the system.
But this might help - on multipoint injection there are two hoses from the air inlet to engine. One goes from the air filter connector to the throttle, to the inlet manifold via an extra air device which is an electric device that provides extra air at startup to provide a faster tickover - it slowly closes as it warms up to prevent a fast tickover when the engine is hot. If this device sticks open you will get the wrong tickover speed.
The second hose goes from the oil filler to the air filter box which is the one you block off I think. Its job is to relieve pressure and vacuum build up in the engine ( and to spray unwanted oil onto the air filter). Some things to check I guess.
Your petrol flooding might be the fuel injector sticking open. You can get them cleaned and checked at an injection specialist.

[MillesimeEnjoyer]

Thank you all very much, i will see if i can clean the injector.

Maybe i will replace the auto-choke (i dont know what its called)

I will keep you all updated

[Jaba]

Thank you all very much, i will see if i can clean the injector.

Maybe i will replace the auto-choke (i dont know what its called)

I will keep you all updated

Auto-choke = the AAD auxiliary air device. You can check it if you remove it. It should be open to air when cold and slowly closes the valve when there is 12v applied via the ignition. Easy to check its operation by clamping the supply hose and noting any change in tickover speed.
As previously mentioned check the throttle flaps for correct closing too.