SMOKEY A4 19 TDI

**BrendanMC** · 17-01-2007,12:26 AM

Hi,
I have recently given up my trusted 1.8 20v A4 for a 1.9 TDI 110 bhp avant. The trouble is the car is smoking under acceleration. Not hard acceleration, that's really smokey, but say climbing a hill and you give it just a little dab more, it leaves a reall trail, rev it slowly and it's fine. Expert on the petrol models, and I am willing to share my three year experience on the 1.8, but I'm new to deisel.

**AudiSport** · 17-01-2007,08:50 AM

I used to have a 110 GT TDi Golf and that was just the same. I remember being somewhat worried about the smoke myself at first, however after some research and chatting with others I just put it down to the fact it was a diesel!

Has the car been re-mapped?

**Dave Avant** · 17-01-2007,05:45 PM

Check airfilter for being dirty or clogged.
Clean Maf sensor with electrical contact cleaner.
Disconnect EGR valve.

My Avant did a bit a smoke under accelleration more so when the engine wasn't fully warm, now with the above looked at, no smoke.

**BrendanMC** · 18-01-2007,12:34 AM

Thanks for that, but guess what happened today. I went out in the car for a 20mile journey, gave it a little dab at a junction and ended up driving for 18 of those miles in limp mode, ie no turbo. then restarting the car some 6 hours later it ran great. Now I'm being told by my local audi specialist that it's either the £80 MAP sensor, which may well be ok with just the clean Dave was talking of or it's a full blown £700+ turbo. VAG COM fault was intake manifold pressure-sensor-(G71) short to B+. I'll try the cleaning of it first, now I'm very reluctant to rev the beast. But i will try all of above before i go for the turbo.

**auiron** · 18-01-2007,12:51 AM

Hi, If it happens again, check the "crank case breather", as it could have been unblocked and may block up again.

**Dave Avant** · 18-01-2007,11:44 AM

There is the;

MAP - Manifold Air pressure - this senses the boost pressure
MAF - Manifold Air Flow - This senses the amount of air entering the engine.

Maf is attached to the airbox and I think the MAP sensor is on the black boost pipe which runs across the back top of the engine. But the fault code reader does say its the MAP sensor.

If the fault is intermittent then its unlikely to be the actual turbo as its a mechanical device and if its broke, its broke.

**S2AVANT** · 18-01-2007,12:31 PM

Your turbo can't have fixed itself overnight, so don't be led down that path.
There is a N75 valve on the AHF engine which gives these symptoms when it's tired. They aren't cheap.

It controls the boost that the engine gets. It lives on the bulkhead and has loads of vaccum hoses going to it. Check the hoses as they can rub and wear through.
I had this problem on the A3 110 tdi and your engine is basically the same but longitudinal. Our problem was the hose had worn a hole in itself. Its 4mm vacuum hose, you can get it from GSF.
The smoking issue is probably due to a worn out MAF.
If your car isn't using oil between services then the black smoke is unburnt diesel, due to the MAF giving the ecu the wrong information.
You can get a Pieburg (mercedes) MAF off Ebay for ~ £35.
Do a Google search for a comparison of their outputs compared to the Bosch unit. There is hardly anything in it.
Good Luck, and don't buy a turbo just yet.

**Dave Avant** · 18-01-2007,02:27 PM

As above if the actuator pipe has a hole it won't be able to open the wastegate on the turbo allowing it to overboost which the ECU will recognise giving a warning or maybe a limp home mode.

S2Avant,
re MAF; Is it universal then the Pierburg? The casing could be different but I know the actual sensor can be removed from the inlet housing. Just wondering.

**S2AVANT** · 18-01-2007,03:05 PM

Originally Posted by Dave Avant

As above if the actuator pipe has a hole it won't be able to open the wastegate on the turbo allowing it to overboost which the ECU will recognise giving a warning or maybe a limp home mode.

S2Avant,
re MAF; Is it universal then the Pierburg? The casing could be different but I know the actual sensor can be removed from the inlet housing. Just wondering.

The sensor is swapped into the Audi housing. I think they have done some digging and found which Pieburg is equivalent to which Bosch MAF sensor. When I need one I'll be getting one from there.