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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. :D

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
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.

Dave Avant
18-01-2007, 04:11 PM
Thanks, handy to know, just incase.

BrendanMC
18-01-2007, 11:08 PM
OK guys, plenty of food for thought, but her is the Audi Specialist's view, for anyone else with this problem.
the MAP sensor which does live in the back pipe from the intercooler does actually read the manifold pressure and sends the signal via the ECU, which controls the wastegate, ie the boost. But what i'm told is that the fault i got is due to either a faulty MAP sensor, giving false readings ot that the wastegate is sticking. if it's the sensor then fair enough £80 or so. and substitution is the only way to really find out. If it's the waste gate sticking then it could be a one off or the start of the end. Seemingly if you can get a hold of a vacuum gage or similar device and check the action, in both directions, of the wastegate, it has to be smooth without any binding or sticking. And you can clean the MAP sensor. So i'll start with the electrical cleaner, and let you guys know how it goes. OK!

BrendanMC
27-01-2007, 10:45 PM
Hi, I'm back. Ok here's the deal, I cleaned and checked all of the vacuum pipes, cleanned the Air Intake temp sensor and pipe. Used an electrical tester on both the EGR solinoid and the Turbo acuator valves. Vacuum tested the EGR Valve and the Turbo variable wastegate valve and all is well. The valve is not sticky and action is smooth in both directions, yet once at 2400 revs for 4 or 5 seconds you can feel the turbo go and the car stays in limp mode till the ignition is switched off. It's got me baffled, and it runs great below those revs, use the gearbox and it's fast and smooth as silk, approx 47 mpg too.
What is this?????????????
OH just for info, I don't know where the smoke has gone, i haven't seen a puff since it started this limp modse carry on. I wonder if this is a clue as to what is wrong.
Help.

madfella65
29-01-2007, 02:30 PM
BrendanMC - exact problem that i had order of events below;
Driving home one night (actually xmas eve!) passing a car ~50mph and..... nothing no power - the car felt like driving a 1.0 Diesel (non-turbo!)
Stopped the car and started it again - drove like mad - no problems... until about 5 minutes later same prob no power - left it over xmas - then took it to a mate who is a vw/audi mech found a vacuum pipe which had been cut (didnt really explain the intermittent problem - happy enough to fix it and hope it was the solution!)
About 2 days later (not much driving done over xmas as you can imagine) problem arises again.
Back to the drawing board (intermittent pressure on the vacuum pipe to the turbo) - mate happened to have an N75 (small solenoid valve that bolts on to front of engine) changed it - not really much difference - put the old one back is it wasnt faulty - then to the MAF (he also has an A4 B5 one) swapped with his car - no difference
B5 MAP wouldnt fit from his car - so brother has a 150BHP golf tdi - swapped with his - cha ching! solved - car never went as well!!!!
Also - i think there is another sensor right down on the top of the intercooler which could be your prob - this is another sensor that feeds air temp or something back to ECU

Hope this helps you get to the bottom of your prob - if you know anyone with the same car as you MAP & MAF sensors take 30 seconds to swap (two star head screws)
Can post pics of their location if you need it?

BrendanMC
29-01-2007, 06:57 PM
Thanks for that.
I ordered a new MAF last night, i thought it might be that especially as the car went from quite smokey to really clean but cutting out.
I'll cross my fingures and post the result.
Thanks again.
PS is the N75 valve the black and white one that only allows vacuum in one direction. I've heard it mentioned so many times yet haven't seen this elusive character.
Brendan

VW Techniker
29-01-2007, 08:38 PM
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.

MAP - Manifold Absolute Pressure
MAF - Mass Air Flow

madfella65
30-01-2007, 01:31 AM
181 Maf

182 Map

183 N75 (one on your car is black and white and located on the front of the engine quite close to the A/C compressor)

Dave Avant
30-01-2007, 11:54 AM
MAP - Manifold Absolute Pressure
MAF - Mass Air Flow


:p :D

andyroo
03-02-2007, 11:45 PM
Hi Folks
My A4 1.9 130 smoked very badly under hard acceleration just fitted a K&N panel filter and wonderous things NO smoke at all now (no gains in performance but that does not surprise) maybe thats all thats needed!!:biglaugh:
Always pays to try the cheap solutions first!!

Dave Avant
04-02-2007, 01:59 PM
Hi Folks
My A4 1.9 130 smoked very badly under hard acceleration just fitted a K&N panel filter and wonderous things NO smoke at all now (no gains in performance but that does not surprise) maybe thats all thats needed!!:biglaugh:
Always pays to try the cheap solutions first!!


I've fitted a K&N panel filter (washed it first to get rid of excess oil, so not to foul the MAF) and disconnected the EGR, no smoke at all.

andyroo
05-02-2007, 09:35 PM
Hi
Washing the filter defeats the object. The oil is there for the muck to stick too. If there's no oil there's no stiction and therefore no filtering of fine particles only big lumps!!

Dave Avant
06-02-2007, 11:37 AM
Hi
Washing the filter defeats the object. The oil is there for the muck to stick too. If there's no oil there's no stiction and therefore no filtering of fine particles only big lumps!!


Yeah, but I didn't totally clean it, just a quick clean to remove the excess. But after you have done a few 1000 miles, whip out the MAF and clean it, you'll probably notice an improvement as it may have a coating of oil on it. Unless you drive in dry dusty environments then getting rid of some of the oil won't do any harm. :D

BrendanMC
23-03-2007, 08:15 PM
Hi Guys,
remember my problems.
I got to the end of it, but feel I have to share the fix with you.
First i have to tell you that i only got the car in December and it had a new timing belt fitted prior to my picking it up, so as we all know the front panel would be put into service position for this.
Anyway, sought loads of expert advise as to why my car was going into limp home mode, had all sorts of answers from the ECU being gubbed to, the MAF, MAP, temp sensors and even a new turbo. so a new MAF, n75 valve and almost £200 lighter and still no joy.
Then a guy tells me i have a leaking turbo pipe, a visually checked them all, to find only a slight seepage of oil where the turbo pipe joins the metal pipe that runs through the front bumper. Anyway the clip tightened a good few turns and i thought problem solved but no. But when I inspected it again a little more seepage, the pipe has a concafe part which runs along it and the turbo pipe had been pushe too far onto the metal pipe, therefore was not sealing on the flat underneath, loosened it moved it back two inches and hey presto, easiest cheapest fix I ever had on an Audi TDI. So if after a service or removal of the from bumper your car does what mine did you now know exactly how to fix it.
Thanks for all your help and ideas.
Brendan

BrendanMC
04-04-2007, 10:59 PM
My previous reply was all rubbish. The car went into limp mode a few days later. This time i decided to get my hands dirty and find out exactly what the problem was. I started by getting some details on the turbo and attached a vacuum pipe to the vacuum control unit at the top of the turbo, I now understood how this turbo worked, or should I say, how it was supposed to work. I applied vacuum to this pipe, via the old gob and without the engine running, while having a good old grop arround the actuator control rode, the problem was so abvious. The movement of the control rod was so limited, I would say approx 40% or so. When vacuum was applied it moved up, increase in boost, but failed to go all the way to it's stop, in fact quit a bit away, i could get it all the way but only by using my hand too, and it really was sticky, anyway when vacuum was released the rod returned slowly but again no where near it's full stop. So after going in both directions for maybe half an hour i was getting nowhere. I had to get the turbo cleaned as easily as possible, and went about looking for a simple way to do this. Then I saw my problem solved, I could get to the turbo viens through the EGR Pipe, but what would i use, I know redex. £3.99 and ten minutes later i had removed the EGR pipe at the EGR Valve and proceeded to pour 1/4 of the bottle of redex in, then i applied the vacuum again tp the pipe, hey, the rod came all the way up till the stop, and when vacuum was released, it didn't return slowly but at a very fast rate. Bingo. So in went another 1/4 bottle and i left the car for an hour, refitted the original vacuum pipe and the EGR pipe, which took all of 5 mins. The car now goes like it never did at least with me before, smoother, faster and so much quiter. Considering I was ready to go the £731.00 for the new turbo and £150 to have it fitted. I recon this is a right result. So if you have the same turbo as me, get some redex into it, you could save a bloody fortune.