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Matt, Engineer
Category: Car
Satisfied Customers: 20396
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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Hi ihave a citroen relay 1800 td hdi lwb..smoke..driving along..speeds

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Hi ihave a citroen relay 1800 td hdi lwb and has developed a problem of excess exaust smoke when engine is ideling or when sitting at traffic lights etc .Engine is allright when driving along at all speeds ..There is only about 58600geniune miles on clock .Have you came across anything like before or can you advise me what can be done to overcome this problem.
thanks stanley .
Submitted: 5 years ago.
Category: Car
Expert:  Matt replied 5 years ago.

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

The other possibilty 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

Edited by 350Matt on 2/2/2011 at 8:36 PM EST
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