Black smoke, excessive fuel consumption and lack of power.

HomerSimpson · 12-04-2009,09:42 PM

Hi all,
I have a problem with my 98 1.9 A4 TDI, it is throwing out a lot of black smoke and using an excessive amount of diesel. I would say in the region of 25-28 miles per gallon, it also has a lack of power and under load the engine revs seem to surge, a bit like putting the brake on and off rapidly. i was told the MAF was cream crackered and to this end I have replaced it TWICE!! It actually seems to run slightly better with the old one. I am getting fed up of having to ring up and say that the MAF is faulty and get a replacement. When I fitted the first replacment it seemed to run OK for a day then it was back to chucking out smoke etc. Is there any other fault that can cause these problems or am I just unlucky and getting duff parts??? All help will be gratefully received.

**davidfbmw** · 12-04-2009,10:05 PM

have you changed air filter recently

**kenney** · 12-04-2009,10:11 PM

Hi Use only a VW, MAF

HomerSimpson · 13-04-2009,08:41 PM

Thanks all for the replys.
The air filter was changed about 3 weeks ago, just after the problem started, as this was my first thought as to the problem. Looks like I will have to bite the bullet and get a genuine MAF, OUCH!!!! Mind you it will cost me more in damned postage sending the faulty ones back if I continue the way I am!!

Once again many thanks.

**Dozy** · 14-04-2009,08:30 PM

Hi Homer

I had a similar problem on my last audi : was traced to a leak in the boost pipe. Engine was getting the right amount of diesel but the air to burn it wasn't making it to the combustion chamber, hence the smoke. Suggest you have a good look at all the boost / intercooler pipes for leaks / splits / loose connections. Hope you get it sorted soon.
Cheers
Dozy

**bohoo** · 14-04-2009,09:51 PM

it could also be your turbo boost sensor sticking. if it was stuck partially open it would give of dark smoke under heavy pedal. would also give you a flat spot arround 40-50 mph

**jonnyforman** · 14-04-2009,10:22 PM

i had a similar problem crap fuel and no power! check the cables coming from you control unit leading to your turbo, one of the wires had snapped on mine so it wasnt giving any turbo out whatsoever, bit of soldering soon sorted that and everything was back to normal, also check your boost pipe aswell as mine had split too hope that helps

HomerSimpson · 15-04-2009,12:07 AM

Cheers all,
Will check all the pipes etc, however I think it may be the MAF as it is only an OEM part and when I fitted the first one it ran like a dream for about a day!!! Then it was back to chucking out smoke etc, and it does seem to run better with the original, that is still rough but better than the OEM part. It is running like a bag of broken spanners at the moment, seems to idle OK, but at speed feels like it is missing quite rapidly. Have spoken to the brother in law, who is a mechanic and his gut feeling is that the MAF is faulty. He is going to have a look next week when I get to see him so hopefully we can get it sorted then, but will keep posting till the problem is solved.

**bigdee** · 15-04-2009,04:40 AM

sounds like your MAF meter to me m8, its a very common problem with audi motors for this to pack in unexpectedly and there are a rake of different symptoms to go with it the most common being complete lack of power, Any ones ive replaced for people are straight from my local breakers as there a fraction of the price but as the other guys say, just give all those hoses a quick check over, it will only take 5 mins and it will keep you right, Good Luck m8

HomerSimpson · 03-05-2009,03:17 PM

Hi all,
Just a quick update as to progress, have changed the maf for an original and the power is back up to where it was, also it has cured another problem I had with the engine going over 3000 revs under load and the engine going into limp mode. However the fuel consumption is still high-ish and it still chucks out smoke under load. Brother in law checked it with a vag-com and said it was the Maf, he also said that it might be worth dosing it with a diesel additive to give it a clean out which should stop the smoking.

I am planning to check the pipes myself, however I am not sure which ones I need to be checking! Any help as to which ones would be gratefully received. I guess one of them is the one that has the gauze like covering on it, is that the turbo boost pipe?

Thanks again for all your help, hopefully after this I can close this thread.