Golf 4 AXR springt spor. nich an | Posts 16+

vagtuning wrote:

since then, it's been a week without errors...today it happened again....30 seconds of sputtering at the gas station.

Here it is again, that "workshop happiness" phenomenon:
When the situation is unclear, and you suspect something might be wrong, you might end up replacing or repairing something, and yet, the error disappears for a while: How can that be possible

ulf wrote:

Here it is again, that "phenomenon of workshop happiness": When the situation is unclear, and you suspect something might be wrong, you might end up replacing or repairing something, and yet, the error disappears for a while: How can that be possible

It's almost a philosophical question. I imagine that when troubleshooting, you check every suspicious spot by tapping, wiggling, and pulling. This temporarily fixes any external and internal loose connections and oxidized electrical contacts on cables, connectors, and within the sensors, usually for a week or two, until the old problem reappears. The bill has already been paid.

Sincerely,
Christian

Bertil wrote:

NW sensor check... if it's faulty, the PD starts extremely reluctantly. It would have been a miracle if it were the crankshaft position sensor.

Okay, I agree with that so far - but how does that explain the organ concert called "Null Kompression" (-> see the original post)?

ulf wrote:

... but how does that explain the organ concert "Null Kompression" (-> original post)?

... I have no idea... My AXR does something similar if I prevent it from starting (see above). I can't explain this effect.

Bertil wrote:

My AXR behaves similarly when I prevent it from starting (see above). I cannot explain this effect.

It's a shame that you can't see the valve position from the outside with the AXR engine - and I suppose you can't read it out using VAGCOM either, right?
For all other actors, we can log various data .

Do you actually have an LDA (Lambda Probe) installed? Or, are there also relatively simple ways to tap into the pressure behind the throttle valve, similar to how it's done with the membrane pressure control flange on EU3 TDIs, in the throttle valve-AGR (Abgasrückführung) units?

ulf wrote:

Bertil wrote: My AXR behaves similarly when I prevent it from starting (see above). I cannot explain this effect. It's a shame that you can't see the valve position from the outside with the AXR engine - and I suppose you can't read it out using VAGCOM either, right? For all other actors, we can log various data . Do you actually have an LDA installed, or is there, like with the throttle valve-AGR units, a relatively simple way to tap into the pressure behind the valve, similar to how it's done with the membrane dosing hold flange on EU3 TDIs?

I don't have LDA installed. I don't have space for it.

Do you mean the DK (Direct Kernel Object) could be closed during the startup process?
This can be checked with a simple multimeter. The flap is controlled via PWM, similar to the switchgear in the VP ESP. The DK drive must be a magnetic coil drive.

The DK (likely referring to a specific component) is an emissions-relevant part. These parts are all monitored by the MSTG (likely an abbreviation for a regulatory body). If the sensor is in the wrong position, it will immediately generate an error code (as required by the EU4 OBD2 standard).

Quote:

The DK (Diesel Particulate Filter) is a component that affects exhaust emissions. These components are all monitored by the MSTG (Motorfahrzeugsteuergesetz). If it is hanging in the wrong position, it will immediately generate an error message (as required by the EU4 OBD2 standard).

Even if the engine isn't running yet?

Then we could try to trigger this forced error code.

- Ignition on.
- The flap is now positioned vertically in the airflow (so it's easily accessible).
- Flick the switch with your finger.
(Hopefully, the force driving the flap is not stronger than its bearing ).

Now, the actual position should deviate from the desired position, and there should be an error.

If that's the case, it will likely only be monitored during runtime, which means it could hang during startup without setting an error code.

m;

dieselmartin wrote:

The flap is now positioned vertically in the airflow (making it easy to reach)

Hmm, with horizontal flow, it's probably more likely to be horizontal - but in any case, "open."

Quote:

If not, it will probably only be monitored during runtime - so it could hang at the start without setting an error code.

There's still the "Orgeln" (presumably referring to a specific type of equipment or system) between the "Stand" and "LL" (likely abbreviations for different locations or systems) – this should also be included in the check.

But let's think of something else:
We have this ridiculous invention called LMM on board.
With the throttle body open and the injector speed set, the cylinder filling (which can be read out using VAGCOM!) should be approximately the same as the low load value without EGR (around 400 mg, if I recall correctly).

Usually, the engines start up too quickly to get a somewhat stable reading.

If an AXR unit sometimes refuses to start reliably and makes no compression sound, it might be worth logging the air pressure during operation.
If the results are only fractions of the normal value, it suggests that the DK (presumably referring to a specific component or system) is closed.

It sounds best when aligned with the airflow - I didn't express myself clearly before.

Is there no visible external axis on the DK (presumably a device or component) to which one could attach some kind of indicator – for example, a small flag that would display the position, similar to an analog gauge?



m;