Superb (AVF, 1.9 TDI with 130 hp), fuel injection quantity too high

Greetings, community.

I'm trying to help a taxi colleague with his application for vocational training (AVF), but I'm stuck and can't seem to make progress.
He had a problem after a DIY timing belt replacement: the car was shaking violently and had very high fuel consumption. He also consistently receives error messages indicating that the boost pressure limit has been exceeded and that the exhaust gas recirculation system is operating beyond its specified limits.

I then checked the engine using the MWB 4 diagnostic tool and saw that the valve timing was outside of the acceptable range. I advised him to have it readjusted.
Even after having another mechanic adjust it using shims, the symptoms persist.

In MWB 4, the subsidy now starts at 1.5 volts. OT, synchronization angle at -2.5°, which is within the tolerance. However, the boosting duration is still fluctuating at 8.7° KW (target value: max. 8° KW).
The injection amount is 14.5mg per injection (target: 3-9mg per injection), and the air mass value at idle is 400mg (target: 400mg, but the target value according to the label is approximately 300mg).
Boost pressure in the LL (likely referring to a specific system or component), target: approximately 1150, actual: 980.

Now we know that the values are not correct, but I have no idea what the cause might be.
The air mass meter should be working correctly if the target and actual values are in agreement. Why is the engine control unit (ECU) sending him a higher target value?
The LMM is correctly regulating the required setpoint, but the setpoint is approximately 100mg higher than it should be.
The biggest deviation is, of course, in the amount of fuel being injected, which is about twice as much as it should be.
Hopefully, you can help us a little.
Greetings.

Serdar.

Hello,

Quote:

Injection volume at 14.5mg/dose

If the engine was running at operating temperature, the air conditioning should be off, and no major electrical devices should be in use (or the battery is drained), then this is too much.

First, using VCDS, check the synchronization angle in measurement block 1 of the engine control unit. Have you already done this, and is it okay? Are there still any issues with the belt drive that could be causing the higher fuel consumption? Are the bearings of the tensioner pulleys, idler pulleys, and water pump in good condition?
Are the AC unit and AC compressor (or compressor coupling) working properly?

What is the idle speed control system like (according to MWB 13)? "Pre-charge pressure of the tandem pump is okay, no air in the fuel supply?"

Quote:

Turbocharger boost pressure exceeded limit and exhaust gas recirculation, control limit exceeded.

VTG (Variable Turbine Geometry) choked with carbon deposits, wave bearing damaged (error exceeds limit), EGR (Exhaust Gas Recirculation) valve leaking/malfunctioning due to carbon buildup?
It might also be worth checking whether the vacuum hoses (for whatever reason) were disconnected during the timing belt replacement, and possibly... The AGR/VTG connections were reversed.

Best regards, Rainer.

Hello Rainer,

So, the synchronization angle was over 8° KW during the first belt replacement – that's why I advised him to have it adjusted again.
Currently, the synchronization angle is between -1.5 and -2.3° KW. The tolerance range is between -6 and +6° KW. According to that, he should be okay now.
As I mentioned, the duration of the funding is still slightly outside the acceptable range.
I also checked all these values using transaction code MWB0, which provides an overview of all relevant values. "There, the air mass, fuel injection amount, and delivery duration were all outside of the tolerance range, while all other parameters were within range."

Regards,
Serdar.

dieselschrauber wrote:

Hello, Quote: Injection volume at 14.5mg/dose If the engine was running at operating temperature, the air conditioning should be off, and no major electrical devices should be in use (or the battery is drained), then this is too much. First, using VCDS, check the synchronization angle in measurement block 1 of the engine control unit. Have you already done this, and is it okay? Are there still any issues with the belt drive that could be causing the higher fuel consumption? Are the bearings of the tensioner pulleys, idler pulleys, and water pump in good condition? Are the AC unit and AC compressor (or compressor coupling) working properly? What is the idle speed control system like (according to MWB 13)? "Pre-charge pressure of the tandem pump is okay, no air in the fuel supply?" Quote: Turbocharger boost pressure exceeded limit and exhaust gas recirculation, control limit exceeded. VTG (Variable Turbine Geometry) choked with carbon deposits, wave bearing damaged (error exceeds limit), EGR (Exhaust Gas Recirculation) valve leaking/malfunctioning due to carbon buildup? It might also be worth checking whether the vacuum hoses (for whatever reason) were disconnected during the timing belt replacement, and possibly... The AGR/VTG connections were reversed. Best regards, Rainer

Hello again

Okay, so the EGR valve is new, the turbocharger was "cleaned" at some point, and the air conditioning compressor is also working fine.
The LL-roughness regulation should also be fine. However, sometimes cylinders 2 and 3 have higher values. Cylinder 3 occasionally goes slightly outside the tolerance range. Overall, all the values are trending towards 0. Therefore, everything is being handled correctly.
What I could ask him is whether he actually had the tensioners and guide rollers replaced as well... I'm not sure about that.
The values were all measured with the engine running at operating temperature, with the air conditioning both on and off.

Regards,
Serdar.