Exhaust smoke (black) when accelerating

[FAB]

I've recently bought a 2000 Bora 1.9 TDI. After a week or so, I noticed plumes of black smoke from my exhaust when I accelerated. Being a total novice when it comes to engines (or anything electical, mechanical, mathematical .....) I browsed the net for possible causes and had the fuel injection system purged by a local mechanic believing blocked valves to be the most likely cause. Things have improved but the problem has not totally gone away. I still see a plume of black smoke behind me when I accelerate, especially when I accelerate suddenly. I'm told some smoke is normal for diesels but I haven't see any other 'smoking' TDIs on the road. The car otherwise drives fine and I haven't noticed any abnormal engine oil consumption after having driven it for 5000 miles. Any suggestions???

[Alun]

Have you tried getting the fuel mixture set correctly? Diesels normally do chuck out black smoke, but if it's chucking out big thick quantaties of the stuff, maybe the fuel mixture is set too rich? thus getting more fuel in and throwing out thicker smoke. I presume anyway!

[FAB]

Thanks for the tip. You could be right as motorway mileage is a bit lower (44-45 mpg) than what I would expect with my style of driving. It'll be due for service in a couple of weeks and I probably will wait till then before doing anything about it. For the moment, I've switched to BP Ultimate diesel to test out its claimed 'cleansing effect' and improved engine performance. The only thing I've noticed so far though is a much higher pump price. Just out of curiosity, how big (or small) a task is it to adjust mixture settings? Will it require the dreaded main dealer visit?

[Alun]

Hi there,

Adjusting the fuel mixture is simple. I'm not sure how it all works on todays modern engines, but on the older carb fed engines (without fuel injection), it was a simple turn of a screw. I should imagine it differs on todays engines. Your best bet is to wait untill it goes in for a service and just mention to the dealer/garage that you think the fuel mixture is wrong. It wont set you back alot. If I remember corectly I once got the fuel mixture set on an older car of mine and it only set me back £10-£15, so I wouldn't worry too much.

If the fuel mixture is a bit rich then the only problem with that is that you will use a bit more fuel. It's nothing major though.