Golf TDI: Power Loss Troubleshooting

Hello!

Perhaps you can help me. On my Golf (Golf III, engine code 1Z), I sometimes notice that I can't rev past about 3200 RPM on the highway. The speed limit is reached at around 140 km/h. When I accelerate fully, there's a slight hesitation or jerking. This problem comes and goes. I had the error memory checked, and the following code came up: Error code 550, fuel injection timing control, malfunction, control difference - intermittent.
It has also been observed that the BKV (presumably a component) is not doing anything. Could it be that there is a vacuum issue, since the vacuum is also used for boost pressure regulation, right?
Thank you for your help.

Best regards, Martin.

The trail is good.
Check the vacuum, use a pressure gauge!
Check the hoses, including those connected to the turbocharger and pneumatic valves, as well as the U-shaped connectors.
A plastic pipeline to the BKV is also a potential option.

Okay, so I've checked the following: I disconnected the hose directly from the vacuum pump, and sure enough, there's vacuum there. A hose runs from the pump directly towards the interior (presumably for the air conditioning), and another one goes to the EGR valve. I tried sucking on the hose from the EGR valve, but I didn't hear anything. It's possible that this hose is blocked, which could be causing a lack of power at higher RPMs.

Intact cans are sealed and airtight due to the membrane. Everything around the can should be sealed. Perform a syringe test. If it's not airtight, you've found a leak.
The vacuum level, which should be between -0.6 and -0.9 bar, should be maintained for a certain period of time (with the engine off).

"He maintains the vacuum, which I noticed when I disconnected the hose from the pump while the engine was idling. I thought maybe the EGR valve wasn't closing properly. Because if you suck on the hose connected to the valve, you should hear a clicking sound, right?"

You can't create a vacuum of 0.6 bar by sucking with your mouth!!
and it barely makes a sound when it happens.
Put some cream on it, I wrote it.
It is still possible that the EGR valve is not sealing properly when closed. In that case, you should remove it and inspect it.
"The species should really comment on the changes in the 8-meter wind tunnel, specifically how they are manifesting. It could be due to insufficient airflow because exhaust gases are being mixed in after the mass flow meter (MFM), which prevents them from being accurately measured by the MFM."

Hello!

"Today, I removed the EGR valve and tested it with a syringe. It opens and closes perfectly. However, I've now disabled the EGR valve, so it's definitely closed. After a test drive, I'm still experiencing the same problem: I can't exceed 140 km/h or 3200 rpm."
What else can be checked without a VAG-COM diagnostic tool? Could it be related to the bypass valve? It feels like it's filling up somehow when I'm giving it full throttle, almost like someone is lightly rocking the accelerator pedal.
Thank you for your efforts.

Best regards, Martin.

Now it seems like you've reached a point where only the measured data will really help you progress.
So, you can either go to a trusted dealer and potentially pay a lot, or you can buy a VAG-COM device and read the data while driving to see if the mass airflow and air pressure correspond to the expected values, etc.
I hope you've looked up "loss of power" and read about it... Make an effort to search and pay less.

martin87 wrote:

Hello! Perhaps you can help me. On my Golf (Golf III, engine code 1Z), I sometimes notice that I can't rev past about 3200 RPM on the highway. The speed limit is reached at around 140 km/h. When I accelerate fully, there's a slight hesitation or jerking. This problem comes and goes. I had the error memory checked, and the following code came up: Error code 550, fuel injection timing control, malfunction, control difference - intermittent. It has also been observed that the BKV (presumably a component) is not doing anything. Could it be that there is a vacuum issue, since the vacuum is also used for boost pressure regulation, right? Thank you for your help. Best regards, Martin

How many kilometers does it have? In the 1Z engine, the turbocharger boost pressure is not regulated by the vacuum system, so it's not related to a faulty BKV (boost control valve). If the error code "Error code 550, injection timing control, function faulty, control difference - intermittent" keeps appearing, it could be that the diesel filter is clogged (have you tried replacing it?), or the internal pressure of the pump is too low, or the injection advance adjuster in the pump is restricted, or there is so much wear in the area of the axles of the rollers in the roller ring that these axles have become embedded in the aluminum housing of the pump and can no longer move as easily.

Best regards, Simon.

v6tdiaknfrf wrote:

"How many kilometers does it have? In the 1Z engine, the turbocharger boost pressure is not regulated by the vacuum system, so it's not related to a faulty BKV (boost control valve). If the error code "Error code 550, injection timing control, function faulty, control difference - intermittent" keeps appearing, it could be that the diesel filter is clogged (have you tried replacing it?), or the internal pressure of the pump is too low, or the injection advance adjuster in the pump is restricted, or there is so much wear in the area of the axles of the rollers in the roller ring that these axles have become embedded in the aluminum housing of the pump and can no longer move as easily." Best regards, Simon.

Hi,

Okay, so he now has approximately 104,000 km. I drove on the highway again today, and it worked normally again, I even tried it up to 160 km/h... I don't understand why it happens and then goes away.

I had the same symptoms. In my case, the hose between the intake manifold and the control unit (for measuring the boost pressure) was leaking.

Best regards,

However, this has nothing to do with the start of fuel injection. Either the fuel injection pump is worn out, the needle lift control valve is defective, or the fuel supply is insufficient.

Best regards, Rainer.