My 2006 citreon relay i just brought is blowing black smoke

Hello

If you're getting a lot of black smoke or otherwise then a couple of things are a possibility,

Either a major engine sensor such as the airflow meter or cam position sensor has failed so that the ECU is now overfuelling or injecting at the wrong point and resulting in poor combustion.
The quickest route to repair is to have the car plugged into a diagnostic machine which will read off the fault code stored in the ECU (providing the light is still on at this point) and indicate which sensor has failed or whether the fault is more serious.

You can do a very rough and ready check yourself by unplugging sensors one at a time and seeing if any of them change the driving condition which would indicate the most recently unplugged sensor is the faulty one. This method is not foolproof though and reading a fault code off is the better method.

You can also try resetting the car by removing both battery leads and clamping them together for 10 mins as this will reset everything so if the light re-appears then the fault is still there.

The other possibility is that the fuel filter is blocked so resulting in low fuel pressure and again poor combustion - replace the filter in any case as diesels are very sensitive to this


also check how much oil is going through the breather. If its been overfilled with oil it will also produce surging as the oil finds its way back into the engine