A4 2.5tdi Smoking Cured !

[Phil G Watson]

Just an update on a problem that nearly had me parting company with my A4 2.5tdi Avant Tiptronic.
A couple of years ago I had a severe 'smoking on tickover' problem that turned out to be a blocked breather neck . To cut a long story short , £2 k later at an Audi Speciallist with a new turbo, breather neck and all the ancillaries, problem seemed cured.
Gradually though performance lost it's edge and a different kind of smoking problem started; heavy black smoke on acceleration, particularly visible in the mirror at night in following (and choking) cars headlights.
With 188.000 on the clock, many people were advising me to 'bin it' and although this has been the best car I've ever owned, I was beginning to think so too. However as performance continued to suffer, notable a dip in accelleration when I hit the throttle, and the smoking became embarrasingly worse, I studied all the wisdom in the forums and decided it could just be the MAF meter.
So I gambled £110 at Audi Parts (plus £50.00 surcharge refundable when I take the old one back) - there were Bosch ones on e bay for £160 so Audi wins and you know your getting a part that fits.
fitted the entire elbow with sensor included in literally 10 minutes (1 jubilee clip, two screws, one electical plug) and...wow. What a difference, crisper pick up, smoother tickover, better low down acceleration even from cold.
On the road, for the first time I gunned it, a cloud of smoke...oh bugger I thought, but, it diminished to the point that it has virtually stopped smoking within 25 miles use. I've ordered some Forte Injection cleaner to give the injectors a blast through as a precaution.

For such a small investment I'm absolutely over the moon that this has fixed the problem and given the car a new lease of life.
Just wanted to flag this up to people suffering with similar smoky issues.

Good Luck!

[mikeybutch]

I have the same but a B6 and it has had similar probs which have been largely cured by a new needle lift sensor and more so by a top retiming job after the belts were changed....it was nearly 2 cogs out!It would be interesting to hear if the Forte works cos I would expect the injectors to have suffered

[Phil G Watson]

I was worried more that the prolonged smoke problem may have damaged the cat, what do you reckon the chances are?

[mikeybutch]

Hadnt thought of that .When did yours last have an MOT? Would this show up?

[Phil G Watson]

Sailed through it's MOT 2 months ago; surprised me too!

[spartacus 68]

For best results with Forte, then pour it straight into the fuel filter. Drive it hard in first, second and third gears. She'll smoke like an E-Class Frigate when you floor it, but it won't last long. Replace fuel filter afterwards and top up with fresh diesel. If the car is due a timing belt change soon, then don't attempt this.

Glad the MAF works and problem sorted.

[Phil G Watson]

Just an update - I didn't have time to fill the fuel filter with the Forte product, instead I put a full bottle into a quarter tank of diesel and ran it down the M40 to Guildford and back.
Initially a couple of spectacular smoke clouds on kickdown but by the return trip virtually no smoke and the great news is the old motor has definitely got its mojo back!
Seriously, the combination of the new MAF sensor and the injector cleaner has restored acceleration and brought back that ' I could cruise this at 110 all day if I was on an autobahn (officer)' feeling. A simple and cheap fix that should be first on the list if you think your tdi is dying of old age.

[Phil G Watson]

Oh yes, and as if to say 'don't get too carried away with your success' , on the return trip the right hand windscreen washer jet miraculously stopped working...not both sides, just the drivers side pair! so another little job to do.

[spartacus 68]

Oh yes, and as if to say 'don't get too carried away with your success' , on the return trip the right hand windscreen washer jet miraculously stopped working...not both sides, just the drivers side pair! so another little job to do.

That's an easy fix. Use a needle and gently clean both nozzles. Possibly grit in the water reservoir. Fill the reservoir with hot water and mild detergent and run it through, before topping up with screen-wash and fresh water.

[moose67]

I have just been through a similar experience. I bought my A4 1.9tdi S reg as an emergency buy when my Xantia died unexpectedly. The car looked decent enough for the £750 he was asking and after a quick test drive we agreed on a sale at £700. The car did have a very slight lag on acceleration but he told me this before we set off. I needed a car that day so settled for what I could get.

After about 30 minutes of driving I noticed it was smoking heavily and lacking in power at certain times. I went back to him and said I'm not happy about the smoking and want my money back. He stood his ground with his cries of "sold as seen". After some tense moments I wrangled 300 quid out of him and set off home, muttering to myself for my latest bout of stupidity. As I was driving I realised that apart from the problem with the engine the car was in fantastic shape for the miles (193k). It drove and stopped like a new car. The interior was also in great shape and the only fault was a broken ciggy lighter.

I took the car to a garage for diagnosis and was told that the airmass meter and temp sensor were faulty. Also I was told the turbo was failing and it needed several suspension wishbones and arms changing. It became apparent that the car would be costly to repair. I decided therefore to hunt down another A4 of similar age and keep this one for future spares. After 6 weeks of searching I realised that the cars I was looking at were in no better state than the one I already had. Time was running out, the MoT was looming, that meant I'd be off the road and not able to go searching new cars. For weeks I'd toyed with the idea of fixing up the A4 but each time I came to the conclusion that it will be waste of time and money. It was really annoying me, I knew the car was sound overall, it had the exact colour and specs I would want in a car and the chances of finding another to match was next to zero.

So finally after weeks of mind torture I decided look over the car one final time and see how hard it would be for me to fit a turbo and do the suspension work myself. While looking around I found a big split in the hose that joins the intercooler pipe to the alloy manifold. I put my fingers inside the manifold and found a large peice of carbon wedged in there. I replaced the pipe and took it for a test drive and noticed it was performing much better. I blasted the engine out for a minute or so and cleared out loads of black crap. Took it for another drive and the smoking had virtually stopped altogether. I thought to myself 'this is looking good' so I went and grabbed an airmass meter. Took it for another spin and could not believe the difference, the car had stopped smoking altogether and there was no lag at all.

I couldn't believe my luck, the car drove like new again and was pretty damn nippy for a diesel. Turns out as well that I only need 3 suspension arms, 1x brake pipe, 1x back light lens and a number plate for the MoT. I'm getting all that done along with a service and cam belt check on monday. I'm going to end up spending around £600, but if the engine and turbo don't have any issues for a year I will have had my monies worth. I do feel that the car will go on a lot longer. I have every intention of maintaining it and keeping it on the road for a few years if all goes well.

Cheers