2002 BMW X5 blowing out black smoke

Black smoke means it is running to rich, getting to much fuel for one reason or another. You say a recon engine fitted? What do you mean? Is it the original engine rebuilt or a wrecking yard engine or? Get back to me with some info and we will see what we can do to figure this out.

Hi Racefan966,
Thanks for your quick reply. Yes the engine is from wrecking yard not the original engine.
Thanks

Ok no big deal on that, so its running rich (burning to much fuel). So with that is the check engine light on? What have you done so far?

No check engine sign on the dash board.

Can it be the transfer box. i spoke to the mechanic who fitted the engine and he thats said reason for the smoke?

Transfer box? I would think it must be a sensor or injectors or to long of injector pulse or? Would have to do some testing first. I would start with checking o2 sensors then mass air flow sensor, then the TPS.

I have put injector cleaner in the tank. I will check the air flow sensor.
Thanks.

Ok let me know what you find ok