Excessive smoke on A6 TDI 140PS AEL

Hello everyone,

I randomly discovered this page and am very impressed.
Now, I've regained my courage, and I'd like to briefly describe my problem here. Maybe someone has a new idea for me...

Okay, so: I have a diesel engine with 140 horsepower. The problem is that when I accelerate hard, it smokes excessively. In first and second gear, it leaves a trail of black smoke on the road. Even in sixth gear when I'm flooring it, you can still see smoke in the rearview mirror. Then, of course, it's quite a bit less, because you cover a larger distance in the same amount of time. (But I'll be looking ahead again soon... *grins*)
He seems to be reaching his top speed. The speedometer reads 225, while the onboard computer shows 210 km/h. According to... Apparent speed: 203 km/h... Taking into account the usual variations, that should be fine.
Now, I was at an Audi dealership, where we tested the 1551.
According to the device, everything is okay.
We had the opportunity to replace the AGR (Abgasrückführungventil)... it's now working properly; the MAF sensor (Mass Air Flow sensor) has also been replaced... and it's working properly. There's a valve on the injection molding machine (presumably for controlling the pressure?), but that's definitely not the cause of the problem.

Is there anyone here who might have a tip for me?
By the way, the engine now has 180,000 km on it and is not tuned. I use a K&N air filter. I follow the maintenance schedule. The oil is original. Audi.

Thank you in advance for reading.

Best regards,
Wool

Hello,

First, you should check if the target boost pressure is being reached, or if air is escaping after the turbocharger due to a leak (e.g., a loose hose clamp or a faulty intercooler).
Oil stains are a giveaway here.

Check for leaks, and use a diagnostic tool to verify the fuel injection timing.

Finally, there are the fuel injectors. If the fuel injectors are not properly atomizing the fuel, the engine will also produce more soot.
Under certain circumstances, damage to the pistons can also occur in TDIs.
You can have the fuel injectors removed and tested at a Bosch service center. If you want to drive your car for more than 50,000 km, I recommend replacing the fuel injectors. According to reports in this forum, fuel injectors often show a poor spray pattern during testing when they have reached 200,000 km. Since the fuel injectors should only be replaced as a set and they are not cheap, you need to consider how long you plan to keep your vehicle.

Best regards, Rainer.

Thank you for your reply to my post.
Okay... I want to drive this car for much longer than 50,000 km. It's just a fun car to drive. I drive 120 km every day, plus some private mileage. So, a diesel engine is definitely the right choice. A smaller one would definitely work too, but I just think the A6 (mine is an Avant) is fantastic.
Okay, regarding your suggestion: I'll have someone test the fuel injectors. I know someone at a Bosch service center. He's not the best, but he'll do it for a donation to his coffee fund. If necessary, I will remove the nozzles myself and deliver them to him.

And I will also inquire about new nozzles...if it's necessary...then it has to be done.

Regarding the boost pressure, it is being achieved. And the pressure hoses are also sealed; we have checked them. Sorry, I forgot to mention that.

It might take a little while, but I'll let you know.

Regards,
Wool.

Hello,
I had a similar problem. There was a large cloud of smoke when accelerating, and it also smoked white when idling. I replaced the filter for the crankcase ventilation system, which you can do yourself with a little skill, and the problem was solved. You can test it with a pressure gauge on the oil dipstick; it should be around 500 mBar. However, it's easier to open the oil filler cap with the engine running, and there shouldn't be any pressure on it. I've now disabled the exhaust gas recirculation system in my car, and I hope this problem doesn't occur again.
A6 2.5 TDI, 95,000 km.

Bye Hagen.

wolle wrote:

We had the opportunity to replace the AGR (Abgasrückführungventil)... it's now working properly; the MAF sensor (Mass Air Flow sensor) has also been replaced... and it's working properly. There is a valve on the injection molding machine (for pressure regulation?).

In any case, that is not the cause of the problem.

Hi.

If the EGR valve itself is okay, it can still remain open at full load due to incorrect control, which can lead to soot buildup in the area --> Check the EGR solenoid valve and control hoses for kinks --> consult pneumatic technical articles.

Hello everyone,

I'm pleasantly surprised that even such old posts are still being answered. SUPER


So:

In the meantime (but only recently), I deactivated the AGR system. This made it "somewhat" better, but it wasn't completely gone. Then, during an oil change, I disconnected the pressure hose located at the bottom of the intercooler, and lo and behold... a lot of water came out, which essentially clogged the pressure hose for controlling the magnetic valve for the turbocharger pressure regulation. This water is likely condensation. Since I drained the water, the engine ran noticeably better from the bottom and almost no longer hissed. However, now it's slowly starting again ... sometimes more, sometimes less. However, the water has not reappeared.
I'll check the crankcase pressure.
The fuel injectors have now also been tested. Unfortunately, the Bosch service can only test the first stage. However, that stage is working correctly. I hope that the second stage will also be fine.
Well... that's all for now. Are there any other ideas being considered?

Thank you all, and I wish you a pleasant weekend.

Regards,
Wool.