1.9 TDI rapid power loss, severe knocking

Hi,

I've been reading this forum for years, and thanks to the excellent tips, I've been able to fix my TDI myself every time.
But since that weekend, I haven't been able to make any progress.
My Octavia 1U 1.9 TDI's performance dropped dramatically after the chip tuning. V-MAx only reaches 120 km/h at full throttle, noticeable engine knocking at partial/medium load, not a Russian model.
The engine is now struggling to rev up.

Using VCDS, I read out all the relevant values.
Boost pressure is approximately 2000 / ambient pressure is 1020 > this should be a good match, so I'll rule out the turbocharger for now. The LMM (Mass Air Flow sensor) has been replaced, all filters are new, the oil is new, all vacuum hoses have been tested for leaks, the EGR valve is closing properly, and the wastegate vacuum actuator is working correctly.

The error codes retrieved from the diagnostic system were:

Address 01: Engine Control Module
Label file: DRV\038-906-018-AFN.lbl
Part number: 038 906 018 P
Component: 1.9L R4 EDC, part number G00SG, 1629.
Encoding: 00002
Operating number: WSC 31480
VCID: 2341947E9B45

Sure, here is the translation of the text from German to English:

"1 error found:"
00550 - Injection start control.
17-10 - Rule difference - Sporadically.
Readiness: Not Available.


It is noticeable that the fuel injection start timing at idle is set to > 20 degrees before top dead center (BTDC), which is the case at x RPM. The operation should be performed urgently.

I then checked the timing belt and its markings, which had been replaced approximately 30,000 km ago, and found them to be in good condition.

I suspect a defect in the diesel pump/injector control valve solenoid and would appreciate it if you could take a look at the VCDS log from the recorded test drive, as I'm overwhelmed by the amount of data and the analysis.

Thank you very much.

Hello,

Please definitely use the TDI timing checker function in VCDS to check the setting of the injection pump.

The magnetic valve for controlling the start of injection (which is screwed into the injection pump) itself rarely fails; more often, the cable that controls it is faulty (due to a loose connection).
Ideally, there should be an "electrical fault" in the memory of the engine control unit, but depending on the data, I wouldn't rely on that.

A blockage in the solenoid valve itself is also possible. Without activation (i.e., being energized), a high internal pressure builds up in the pump, which causes the hydraulic injection advance system to shift towards "early" timing (resulting in knocking).

Best regards, Rainer.

Did someone delete my post ?
"Could you check the blue fuse located under the engine control unit? It sometimes blows when there's been improper tuning."
Best regards,

Hi,
The entire issue, as the error message indicates, points to a problem with the fuel injection timing.
I would check in the following order:
- Mechanical adjustment of the ESP (alignment pin) to rule out any coarse misalignments;
- Dynamic control (TDI timing), likely set too early - do not change!
- Test drive with recording of measurement data block four. Measurement data block 004 provides data for: engine speed, target injection start, actual injection start, duty cycle. Unfortunately, that information is missing from the log file.
- Valve resistance for injection start.
- Power supply for the valve (e.g.,). B. in the default state); mass; in the default state, the full battery voltage must be present.
- If so, does the valve activate with 12V (e.g., powered by the battery)?
- Actuator diagnosis: observe the pulsed supply to module MWB 004.
hg
Herbert.

dieselschrauber wrote:

Make sure to use the TDI timing checker from VCDS

.

Hi Rainer,

TDI timing is outside the display range.

I've checked the wiring, re-routed it, and applied tension/pressure -> no change.

The error memory does not contain any indication of an "electrical fault."

"This afternoon, I will be removing the solenoid valve for the injection start control. Can the function of the valve be checked/measured while it is disconnected?"


@klahaui - There's no fuse directly under the STG (Steuergerät - control unit). Are you referring to the fuse located below the control unit fuse in the fuse box (on the left side of the dashboard/cabin)?
They have all been measured and are okay.


Bye.

Jürgen.

Hi,

Quote:

I will be removing the solenoid valve for the injection start control this afternoon. -> Can the function be checked/measured while it is disconnected?

This can also be checked while it is installed, see above.
hg
Herbert.

Did someone delete my post here
'Could you check the blue fuse located under the engine control unit? It sometimes blows when there's been improper tuning.'
Regards

Which fuse are you referring to exactly? And could you explain in more detail why they should be removed in the context of 'terrible tuning'?

I know that Audi vehicles often have additional fuses located directly below the engine control unit.
A few large ones, and then the standard flat fuse cartridges.
To the best of my knowledge, the injection pump relay has a 15A fuse located under the control unit.

Furthermore, I've experienced this twice (once with my own vehicle and once with a friend's), where the fuses blew in vehicles that had been chipped, and very poorly chipped at that.
Otherwise, none of the cars had been moderately or heavily modified, and none were "smokers" (cars that produce a lot of black smoke).

It's also possible that the defect originated from somewhere else, but I didn't find anything to indicate that.

EDIT: And I would explain why they burn out specifically when there's bad tuning by pointing to excessively high resistances in the fuel injector control, as often the fuel quantity is simply and unnecessarily increased.

But just to be clear, this is purely my theory. I wouldn't say it's 100% certain, and I'd be happy to be corrected by someone who knows more about tuning.

Hello,

The duty cycle of the solenoid valve controlling the injection rate is generally limited, regardless of the settings in the associated characteristic curve. If I remember correctly, a duty cycle of 15-85% can be adjusted without changing the limit values.
Even if it's permanently connected to +12V, it shouldn't actually cause a fuse to blow.

I think the issue with failures after bad tuning is more likely a coincidence, because those are often old, unreliable cars where nothing really works properly anyway.

Best regards, Rainer.

dieselschrauber wrote:

... bad tuning is more likely a matter of chance, because those are often junk cars where nothing really works anymore...

Hi,

and right away, a big NOOOOOOO.

The tuning is of the highest quality, but it's designed for city driving and towing, and it has been tested since the warranty expired almost 10 years ago.

I didn't manage to get the magnetic valve working today, and to make matters worse, the WFS (likely referring to a vehicle system) malfunctioned on my TT, which meant I had to take it to the workshop to have it reprogrammed.
At least that went smoothly.

Bye.

Jürgen.

Hello,

The duty cycle of the solenoid valve controlling the injection rate is generally limited, regardless of the settings in the associated characteristic curve. If I remember correctly, a duty cycle of 15-85% can be adjusted without changing the limit values.
Even if it's permanently connected to +12V, it shouldn't actually cause a fuse to blow.

I think the issue with failures after bad tuning is more likely a coincidence, because those are often old, unreliable cars where nothing really works properly anyway.

Best regards, Rainer

That's exactly how I remembered it .

Hi,
There seems to be a misunderstanding.

Quote:

EDIT: And why it would only happen with bad tuning, I would explain by assuming too high resistances in the fuel injector, since usually only the amount of fuel is unnecessarily increased.

They are actually related.
Injection timing adjuster - injection timing.
Fuel quantity setting - Fuel amount.
hg
Herbert.

Thank you, Herbert.
Based on the problem description, it sounds to me like the issue is "no voltage at the fuel injector control valve."
I'm not really comfortable with remote diagnosis.

EDIT: Maybe I'm misunderstanding, but shouldn't the internal pressure in the pump be higher the greater the amount of fuel being used?
So, is it also more pressure needed on the injection molding nozzle adjuster?

/viewtopic.php?t=3195 says:

Quote:

Without tax voltage, the injection control valve remains closed, and thus the hydraulic advance is fully effective, which is approximately equivalent to full load operation. As the tax voltage increases, the injection control valve opens further, thereby reducing the advance more and more. This occurs under partial load or at idle.

Here's the translation:

That

Quote:

strongly suggests that something is definitely wrong

with the system, especially considering the partial/medium load: Either there's a broken cable in the SV valve's circuit, or the valve is stuck closed.

In the 1-3-23 log, the LD appears to be correctly regulated at the top (assuming that MWB 23 represents the actual LD value and the setpoint).
However, the MWB 1 (measured oxygen content) in the area around 4000 rpm (timestamp ~ 45) only shows 16 mg of EM (effective oxygen), which likely indicates that much higher peak power (Pmax) is no longer achievable.
So, you should really log the MWB 8 and check why the EM is being so severely restricted .

Hi,
In the VP37, the internal pressure is generated by the wing rotor pump, so it depends on the engine speed, not the amount of fuel. As the internal pressure increases, it pushes the injection timing control piston against a spring, which advances the injection timing. The pressure on the piston, and therefore the EZP (likely an abbreviation for a specific system or component), is regulated by precisely opening the valve.
The low injection quantity is likely a secondary effect, if it is related at all. Actually, the injection timing is determined by the amount of fuel injected, and it shifts earlier as the fuel quantity increases.
It wouldn't hurt to take a look at the MWB 8, but if the content is the same as for the 1Z engine, it will display things like RPM and engine load (EM). Accelerator pedal position, electronic torque limitation, and electronic smoke limitation.
Conclusions about the cause of the premature start of the injection process should be drawn primarily from the tests with MWB 4 and the valve itself. Whether the problem lies with the valve, the power supply, or the nozzle itself, I'm not sure.
hg
Herbert.

Herbert wrote:

In the VP37, the internal pressure is generated by the wing cell pump, so it depends on the speed, not on the amount of fuel. The low injection amount is likely a secondary effect, if it's related at all.

Yeah, I also suspect that there are two independent issues rather than a single cause.