Troubleshooting Volkswagen Golf 6 TDI 66kW (5K1)

First of all, I'd like to commend this forum and community for sharing so much useful and helpful information. I hope someone here has already encountered a similar problem. I'm hesitant to go straight to the workshop because I can already anticipate the cost in euros. I had already replaced parts based on suspicion until it worked, once with a different car, at a VW workshop.

The problem is that the car constantly enters regeneration mode - after approximately 20 kilometers driven. I observed that the measured soot mass increases rapidly. It rises to about 24g, while the calculated soot mass only increases very slowly, remaining between 1-2g. Once the measured value reaches 24g, it is adopted as the calculated value, and regeneration begins. This is indicated by an increase in exhaust gas temperature to 600 degrees on bank 1, sensor 1 (IDE00167). While driving, the calculated soot value quickly returns to normal, while the measured value decreases very slowly to 15g, then briefly increases again, and then decreases again. But never for such a long duration during the drive (tested for approximately 40 minutes on the highway) that it could complete the regeneration process.

I then drove to a rest stop. I didn't turn off the engine and observed that the exhaust gas temperature remained high. The measured value at idle, with the engine running, quickly dropped to around 7 grams, and then the regeneration process ended (according to the last regeneration recorded by VCDS). I then continued driving, and the same thing happened again and again, just like before. I have already replaced the differential pressure sensor.

The car has 110,000 km and has a good mix of long-distance and short-distance driving (70:30). The oil level is increasing due to the frequent regenerative braking (oil dilution with diesel). I changed the oil about 2 weeks ago when this behavior became noticeable. I also replaced the diesel filter and the oil filter. There is no visible smoke, neither white, black, nor blue, coming from the exhaust. Also während der Fahrt (observed from a following car).

The back pressure fluctuates between 10 hPa at idle and 250 hPa when the engine is running at full load. The DPF reading is at 40g, which is slightly more than half full.

I have reviewed the quantity deviations for the injectors and have the following values available. They jump a lot.

Zy1: between -0.2 and -0.5.
Zy2: between -1.2 and -1.5.
Zy3: between 0.8 and 1.3.
Zy4: between 1.3 and 2.2.

Then I checked the values during the regeneration process, and they looked disastrous.

Zy1: between -6 and -7.
Zy2: between -6 and -7.
Zy3: between 6 and 7.
Zy4: between 6 and 7.

After that, I performed a reflux test (approximately 5-6 minutes).

Injector 1: 75ml
Injector 2: 83ml (this injector was replaced 10,000 km ago).
Injector 3: 80ml
Injector 4: 95ml

The error memory is clear and shows no fault codes. The EGR valve and throttle valve have been tested with VDS and are functioning correctly. The next step is to have the injectors tested. However, could this alone be the cause of the regeneration issues? And, more importantly, where is all this soot coming from in such a short time?

I am grateful for any ideas or help. The error memory has no reported entries and is clear. The AGR (Abgasrückführung) and throttle valve tests with VDS (Vehicle Diagnostic System) are functioning correctly.


Last edited on 20-10-2021, 16:17, edited a total of 3 times.

Hi,

Autoscan?

Best regards, Rainer.

Hello Rainer,

Sorry, I forgot about that one. It's from October 3rd, but nothing has changed. I didn't save the last scan, but it was successful and without any errors.

Hi,

I would be interested in knowing the rail pressure calibration points for all 4 cylinders, along with the corresponding 3 values for each. However, the mean absolute error is no longer the best metric either...

Sure, I'd be happy to translate that for you and post it.

Best regards,
playzocker22

I will read these data and post them. It will only take a little while, as I have removed the intake manifold and throttle body to verschandeln them. I expected the carbon buildup to be worse. The intake valves for cylinders three and four had more carbon buildup than those for cylinders one and two. Everything is verschandeln now, and it will be assembled today.

The return flow test ran for about 5 minutes, and the difference between the lowest and highest readings was approximately 25%. This isn't great, but it's still within the range I've read about. Of course, this doesn't say anything about the spray pattern, which can also lead to poor combustion and soot. That's why my next idea was to have injectors 1, 3, and 4 checked. The second one was replaced at 10,000 km and should still be in good condition.

The AGR valve was replaced by VW approximately 30,000 km ago as a goodwill gesture due to the diesel scandal. I'd also like to take a look, but upgrading this model is quite a hassle.

Okay, so if you didn't get any error codes after the EGR test, then generally everything is fine for now. I've already been through all of this with my P2002 error, which was related to the ND EGR valve. How much carbon buildup there is on the valves doesn't really matter at this point, because the air being drawn in is combined through a single pipe before it splits into sections 1, 2, 3, and 4. It's possible that the design of the part is the reason why 3/4 of them are carbonized.

Return flow tests are indeed not very informative unless you collect a liter of fuel in one minute with a 1.6 TDI engine, or you have 20ml in one container and 250ml in another. However, neither the return flow test, nor the fuel injection quantity deviation, nor the rail pressure calibration points indicate whether a specific injector is working or not (what is meant is that these are only values to be used as a reference for more in-depth troubleshooting, such as injector testing on a test bench). I strongly suspect that at least one of your injectors (and I suspect all of them, including the one you replaced, even though it's an original Bosch part and hasn't been refurbished) is faulty, and significantly so.

Limit values for rail pressure calibration points:

RdKalbrPkt 1: -45 to +45 us.
RdKalbrPkt 2: -15 to 5 us.

The third one shouldn't deviate too much from the second one, or from zero, but it can. It depends on what the other values are.

Reports then

Soot is formed during combustion when there is a lack of oxygen.
Typical cause:
- Charge air leak (insufficient air), visible as oil on the charge pressure hoses.
- AGR leak (exhaust gases instead of fresh intake air).

Since it's occurring within a 20km radius of you, the problem must be significant enough that it needs to be identified quickly.

If it's not due to excessive soot, something is wrong with the measurement. I can't say for sure exactly how the load is determined. However, it likely comes primarily from the differential pressure sensor. You did log it, but unfortunately without fuel injection quantity and engine speed. However, in your measurement, it increases very quickly and evenly until the regeneration starts. It then decreases again during regeneration. For me, this indicates proper sensor functionality.

I would like to read the rail pressure calibration points. However, I don't have access to them in the extended measurement data. Is there another way to query for this information?

Thank you.

Air mass and air mass should be in agreement. Both in the cold and in the warm state.

How can you test for AGR leaks?

"Either you've made a typo, are searching in the wrong control unit, or the Conti Simos PCR2.1 isn't storing these values (which I highly doubt). It's possible that they're just labeled differently compared to Bosch control units (mine, for example, is an EDC17C64)."

You can probably test for AGR leaks in the adaptation settings. There's a test routine (at least there is for me) that you can run for the AGR, which provides a final result. Otherwise, you can use the actuator diagnosis with measured values, where you compare the desired AGR value (AGR SOLL) with the actual AGR value (AGR IST) while the AGR is being activated in 10-second intervals. If the test routine is interrupted, you have a problem. If it ends with "Completed | ---", it usually means there's an error stored in the control unit. If it doesn't start, you must have an empty error log in the MSTG, and the test routine must have been started in the correct sequence.

VCDS settings - connection test - apply - control unit - MSTG 01 - access authorization + code - adjustment - and then you can start. Otherwise, you'll often encounter this error.

"Aborted - Incorrect command sequence" or similar.

I performed the AGR test, and VCDS reported that it passed.

"I took it for a test drive again after cleaning the intake manifold, etc."
After the test drive, I logged all the parameters that VCDS provides in the extended measurement values for the injectors into two separate files.

Hi.

hauminix wrote:

I would like to read the rail pressure calibration points. However, I do not have access to them in the extended measurement data. Is there another way to query for this information? Thank you

.
They should be there...

The tolerances on the injectors don't look good. Are they properly mounted and sealed to the cylinder head?

Best regards, Rainer.

The coding in the control unit matches the deviation codes on the injectors. Tomorrow, I'll remove them and take a closer look. I already obtained the original copper gasket and the O-ring gasket today.

Let's see what surprise awaits me. I will have them checked beforehand and then decide whether to repair them or buy new ones.

Unfortunately, rail pressure calibration points are not available in VCDS. I checked the MSTG (Measurement System Test Group) - advanced measurement values, using the "Rail" filter, but I couldn't find them. I'm using VCDS version 21.3.0. I've also tried it with the English version 21.9.0, but still no luck. It's not available there either.

I've now taken them out and attached the pictures. I was actually expecting something different.

Unfortunately, many of the images are very blurry.

Do you know anyone who has a *good* ultrasonic cleaning device available?

I used this to first verschandeln and thoroughly inspect my injectors after the engine failure. The injector was torn at the top, and the rest of it looked just as corroded.

I find it quite concerning that all four now look like they're not exactly young anymore, especially the one that was recently replaced.


I once removed an injector after about 10,000 km to access the code (which, unfortunately, wasn't visible without removing it), because the workshop hadn't coded the injector.

It certainly didn't look like that yet.

Quote:

The coding in the control unit matches the deviation codes.

"With those codes displayed? Was the replacement injector a new one?" Then it should work, as long as you don't, for example, confuse the numbers 0 and O.
However, in the case of refurbished products, the new code is usually located on a separate label on the side. But I think you would have discovered that at the latest during the expansion.

The margin of error, however, doesn't look good.

The return volume is perfectly fine.

What just occurred to me:
"With two of the injectors, the copper gasket is quite dirty on the contact surface, and the contact surface on the injector head itself doesn't look entirely verschandeln in the relatively sharp images." It suggests a possible leak in the ZK (likely referring to a Zylinderkopf, or cylinder head), which could explain a number of issues.

Regards,

Lukas.

Only injector 2 was replaced (approximately 10,000 km ago) with a completely new one. I have checked all the codes, and they match the MSG.

Here's a sharper image of the copper gaskets.


It probably can't be that leaky, as only slight deposits are visible on the underside of the sealing rings. Above them, they are completely clean. I've seen much worse than that.

The discrepancies in quantities were particularly severe when I initiated a forced regeneration at the station to see how the quantity discrepancies would then manifest. And that's when I nearly fell over.

Zy1: between -6 and -7.
Zy2: between -6 and -7.
Zy3: between 6 and 7.
Zy4: between 6 and 7.

It also runs unevenly when idling, and up to a speed of 2000 RPM; beyond that, it runs better. I haven't noticed a significant loss in performance, either in acceleration or top speed.