peugeot 406 HDi (90bhp) 1999 - black smoke on revving - clamplock
My car failed the MOT exhaust emissions test with a 4.70 reading.It should be below 3.0..As the MOT tester showed me there is a lot of black smoke on revving the car. I had not noticed this before as i drive conservatively keeping the engine revvs as low as possible. There are no other symptoms , the car starts and drrives OK. Could this be the EGR , i ask as i thought a faulty EGR would cause smoke at all speeds..Thanks
peugeot 406 HDi (90bhp) 1999 - black smoke on revving - Peter.N.

If you normally drive the car gently I would suspect that it failed not on smoke but on soot. I drive very much the same myself and this gentle style keeps the flow of exhaust gas low and causes soot to build up in the exhaust system. I always give it a bit of a thrash on the way to the MOT which clears most of the soot out. If I were you I would do the same and get the smoke tested again.

peugeot 406 HDi (90bhp) 1999 - black smoke on revving - clamplock
Well , took the car for a damn good thrashing then drove it into my local gararge (not the MOT place) they then tested it for emissions and though it just failed on the first test they gave it some more revvs and it PASSED OK..
So I'll be off to the MOT place tomorrow , after i give it another good thrashing
and hopefully get my MOT..Thanks for all the help
peugeot 406 HDi (90bhp) 1999 - black smoke on revving - Bromptonaut

Plenty of possible causes but if you drive conservatively soot tends to accumulate in the exhaust system. Take it out and give it some beans - get the revs over 4k a few times. This is sometimes known as an Italian tune up.

Are there any other symptoms apart from the smoke? My similarly powered Xantia (110) started smoking in the summer - but it was the flat spots and hesitancy I noticed first. Split hose in the turbo/intercooler bit of the induction system.

If the 'Italian' doesn't cure it and you're not finding anything obvious than get an Indy or a diesel specialist to look at it.

peugeot 406 HDi (90bhp) 1999 - black smoke on revving - clamplock
No other symptoms at all , starts and drives well, no hesitancy in running..actually after the test covering the ground behind the car was a sooty black substance. thanks for the advice i will try your suggestion
 

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