Golf 4 TDI: Complete Power Loss - Troubleshooting

Hello, I bought a Golf 4 TDI 90hp (ALH) from 1998, with 92,000 km on the odometer, 3 weeks ago. Everything was fine for one week, then suddenly I encountered two problems.

1. Problem: Complete loss of power. It feels like the car only has 50 horsepower. It takes a very long time to accelerate when you floor the pedal, and the RPMs increase slowly. However, exactly at 3000 RPM, it pulls like it normally does. Above 3000 RPM, the full power is back. On the highway, when you floor it, it only reaches a maximum of 110-120 km/h. But if you shift into 4th gear and bring the RPMs above 3000, and then quickly shift into 5th gear and bring the RPMs above 3000 again, it performs normally, reaching speeds of 170 km/h, and could easily reach 180 km/h. I thought it might be the mass airflow sensor (MAF), so I cleaned it, but unfortunately, the problem is still there! I really hope someone else has experienced this problem, or that someone can help me.

"Problem: My clutch isn't disengaging properly... The previous owner was an elderly lady who mostly drove in city traffic. The strange thing is, the clutch only disengages poorly when the car is warm, i.e., after about 10 minutes of driving. It's very difficult to get the first and second gears, and recently, I was at a traffic light and I couldn't get either of those gears in at all... I waited a bit, and then it worked again (embarrassing). And when I put the car in reverse, it grinds and creaks, but only when the car is warm."

My clutch also engages very, very early! As soon as I release it by just 1 cm, it already starts to engage... I don't think that's normal either.

I hope someone can help me.

Best regards,

Your VTG (Variable Turbine Geometry) system is malfunctioning. It's stuck in the minimum position, which is why you're only getting boost at high engine speeds. You need to either fix the VTG mechanism or investigate why it's not opening and closing properly (e.g., check the vacuum hose or vacuum actuator).
If it's a hydraulic clutch, try changing the fluid. Otherwise, the slave cylinder or master cylinder is likely broken.

Reading the logs and error codes would be extremely helpful! Everything else is just pointless guesswork! The clutch, like the previous speaker mentioned.

T3Surfer wrote:

Reading logs and error codes would be extremely helpful! Everything else is just pointless guessing!

That's right!

However,

Quote:

starting at 3000, full performance is restored

, which suggests a weasel bite in the vacuum hose for the VTG adjustment.

Rainer K. wrote:

However, Quote: above 3000, full performance is restored , which suggests a weasel bite in the vacuum hose for the VTG adjustment.

. . . and is considered the most common cause. However, this does not exclude other pneumatic faults or cable breaks on the way to the LD solenoid valve.

Regarding the clutch issues.
Something similar happened to me back then, and according to experts, I was supposed to replace the clutch release cylinder/throwout bearing. Since the transmission had to be removed for that, I also had the entire clutch kit replaced as a precaution.

Before this action, I always suspected there was air in the system. This was mainly because the clutch engagement problems were sometimes present and sometimes not. Either the 1st and reverse gears wouldn't engage, or they wouldn't disengage. Sometimes the gear was already engaged even though the pedal was still fully pressed.
Since I knew that the braking system and the clutch were supplied by the same circuit, I asked my local mechanic to replace the brake fluid and bleed the system.
Unfortunately, the workshop at that time didn't think to bleed the clutch hydraulics along with the rest (did they not know that there was a separate bleed valve for it??? one doesn't know).
As a layperson, I didn't know that, even though it involves a liquid circulation system, it's still two separate systems. The workshop should have known better.

It was only after I reached the point of having the release bearing replaced along with the clutch kit that my suspicion was confirmed.
The clutch disc was like new, the release bearing was tight and intact. Only after we connected the machine to the clutch bleeding valve as part of our final project, did we see that there was a lot of air in the system, and that this was the sole reason for the clutch problems.

Looking back, it makes perfect sense. Whenever there was air in the system, the clutch release bearing would retract, and the gear would engage. If there was already air in the system at that point, it was impossible to engage or disengage the gear.

In short: Before you throw hundreds of euros away like I did, make sure to bleed the brake fluid system, both through the brake fluid reservoir and through the clutch bleed valve.
Only if that doesn't work should you look for other potential sources of error.

Regards,
Serdar.

"I was at the workshop today, and they said the diesel pump is broken... I found that very unlikely. Okay, the car consumes about 1 liter more fuel, and it also starts a bit late, but what does that have to do with the performance?"

Quote:

Reading logs and error codes would be very, very helpful!

If you only repeat what someone else has told you, you're essentially in the wrong place in this forum.

Here, it's all about action, not just talking.