Excessive smoke from 2.5 TDI V6 after cold start.

Heavy smoking from the 2.5 TDI V6 engine after a cold start.

"I'm having a problem that I can't seem to solve. When starting the engine cold, my 2.5 TDI V6 smokes heavily from the exhaust, accompanied by a rough idle and a loud knocking sound. After about a minute, it stops. The maximum speed (230 km/h) is still achievable, and there's no noticeable loss of power when the engine is warm." Here are a few data points:

- Audi A4, 2.5L engine (AKN), 110kW, ETZ Tiptronic transmission, only 94,000 km mileage.

I've already read all the posts that deal with similar problems, but none of them seem to address my specific issue. Here are the things I have already checked, or had checked:
- Injection start timing adjusted with VAG Com: -2.6°. According to Audi, the ignition timing should be set to 2° BTDC (Before Top Dead Center) with a tolerance of +/- 2°.
- Turbocharger and adjustment are OK.
- Exhaust gas recirculation OK
- Pre-glow system complete, including afterglow, OK.
- The fuel injectors, removed from a VW/Audi vehicle by a workshop, should be in excellent condition.

All error logs are also empty (always).
I used to mainly drive long distances, so it didn't really matter much. He's really annoying me right now.
When I start the car in the garage and open the door, the garage fills with so much smoke after two minutes that it's like a tear gas grenade has exploded.

If someone could tell me what else it might be caused by, I would be very grateful.

Hi! Just to let you know: A small amount of blue or white smoke appearing for a few seconds after starting the engine in sub-zero temperatures is perfectly normal. This is a mixture of aerosols consisting of unburned fuel droplets, their cracking products (secondary hydrocarbons produced by the hot glow plug), water vapor, and other substances. It should disappear quickly once the engine is warmed up.

Since your error memory remains empty, I would strongly recommend taking a close look at the glow plug system and the spray pattern of the injectors, which, of course, involves a significant amount of work: both systems need to be tested while they are removed from the engine. You can still do some things yourself with spark plugs, but not with the injectors...

Question: How many seconds does your car 'smoke' after a cold start and when you drive off? My engine's misfires and rough running consistently disappear almost completely within 10 seconds.

Best regards,
Holger.

Au00 wrote:

Strong smoking from the 2.5 TDI V6 engine after a cold start. "I'm having a problem that I can't seem to solve. When starting the engine cold, my 2.5 TDI V6 smokes heavily from the exhaust, accompanied by a rough idle and a loud knocking sound. After about a minute, it stops. The maximum speed (230 km/h) is still achievable, and there's no noticeable loss of power when the engine is warm." Here are a few data points: - Audi A4, 2.5L engine (AKN), 110kW, ETZ Tiptronic transmission, only 94,000 km mileage. I've already read all the posts that deal with similar problems, but none of them seem to address my specific issue. Here are the things I have already checked, or had checked: - Injection start timing adjusted with VAG Com: -2.6°. According to Audi, it should be 2° +/- 2°. - Turbocharger and adjustment are OK. - Exhaust gas recirculation OK - Pre-glow system complete, including afterglow, OK. - The fuel injectors, removed from a VW/Audi vehicle by a workshop, should be in excellent condition. All error logs are also empty (always). I used to mainly drive long distances, so it didn't really matter much. He's really annoying me right now. When I start the car in the garage and open the door, the garage fills with so much smoke after two minutes that it's like a tear gas grenade has exploded. If someone could tell me what else it might be due to, I would be very grateful.

At what temperature does this problem occur? Is the smoke black, bluish, or blue? How long does the misfire and the smoke last when idling?

I also think about the ignition system. You should measure the glow plug currents during startup.

Yes, I would also suggest measuring the current draw of each individual candle as a first 'official' step. However, one should know the typical inrush current of the specific candle type from the respective manufacturer. Incidentally, the current automatically decreases somewhat as the temperature increases. You should observe the current draw for more than 10 seconds. All candles should exhibit the same behavior, including the same temporal pattern of current draw. The current draw is typically in the range of 10-30A per candle, but it depends on various factors.

However, the glow current and its behavior only provide 99% of the information needed to assess the glow lamp system. The final piece of the puzzle is the visual inspection of the glow plugs. I've seen glow plugs where the tip had crumbled off (or possibly melted?). If these types of candles are still drawing normal current, you won't notice any mechanical defect when taking a current measurement.

Hi,
To clarify, the fuel injectors were inspected in a disassembled state at the Audi workshop, and the spray pattern was okay; the injectors were not dripping. I have also checked the glow plugs multiple times in various ways. These are not burned out, they light up simultaneously and evenly, and the power/voltage supply is also okay.