VW Passat 1.9 TDI: Slow & Weak? Fix with Log!

Hello everyone,

After a long time, I have to reach out to you again with a problem.

Our family car (a Passat 3BG Variant, manufactured in 2001, with a 74kW TDI engine) isn't doing what I (we) want it to do .
The entire car feels very sluggish and underpowered. Of course, you can't expect miracles from the 101 horsepower in the Passat, but it seems a bit odd to me. The 101 horsepower in my sister's Golf 4 performs much better (obviously, it's also lighter), but even the overall engine characteristics are much more responsive and have stronger torque.
First of all, I find the responsiveness to be very sluggish, and it also feels very underpowered. Sometimes you really have to think twice before overtaking a truck at 80 km/h, especially when going slightly uphill. While it does eventually reach its top speed of around 180 km/h on the highway, as I said, the torque leaves much to be desired.

The car has been diagnosed several times, but no specific defects have been identified.
The following items were recently updated/replaced:
- LLM
- Air filter
Diesel filters.
- Vacuum pump (was defective and caused issues with the brakes).
- EGR closed.

The vacuum system is working correctly; there are no cracked or damaged hoses, etc. Also, the boost pressure and air mass appear to be okay.

EDIT: Oh, and something else that occurred to me: It sometimes seems as if there's hardly any difference between partial throttle and full throttle. For example, I accelerate with partial throttle to 2500 RPM and then apply full throttle. However, you can barely feel any additional "boost." The accelerator pedal position is definitely being transmitted correctly to the engine control unit, as we confirmed when reading the data.

What specific data points do you need me to record so that I can potentially help you?

Danke u. Regards,
Daniel.

Check the vacuum system, especially the switching valve/vacuum sensor of the EGR cooling system!

Do you mean one of the two pressure transducers or the solenoid valve?

Best regards,

No, what I wrote...

Could you please explain it in more detail or provide a part number? Or could you tell me exactly where the part is located?

Thank you.

@ Rainer
AGR cooling?
Mine certainly didn't!

@ Streetrod
"Since when has the EGR valve been closed, and for how long was the engine running with the EGR valve open before that?"
It might be worth taking a look inside the intake manifold to see if there's anything wrong.
haithamina

I had the EGR valve closed about 5,000 km ago, but it didn't make any noticeable difference. As I mentioned earlier, I recently had problems with the power brake booster, which required replacing the vacuum pump. Since then, the power brake booster has been working as it should.

I'll be able to take a look at the EGR cooling system this evening. If I have installed it, I could potentially test for a faulty membrane in the unit by simply blocking the hose.

Greetings.

Street_Rod wrote:

I closed the EGR valve about 5,000 km ago, but it didn't make a noticeable difference.

The deposits that built up on the intake manifold over tens of thousands of kilometers before closing the EGR valve certainly won't disappear within just 5,000 km -> read the FA (fault code).

Otherwise, monitor: Simultaneously check both cylinder readings (MWB 8 and 10) at full throttle up to approximately 4000 rpm, and then proceed based on the results.

Hi,
I doubt you have an EGR cooler. Mine is from 2003 and doesn't have one. But it seems more likely that the goal is to draw your attention to the EGR system and/or the intake manifold. As I already asked: with 100,000 km of city driving, a functioning EGR system, and oil leaking into the intake manifold, the passage could be severely restricted. 5,000 km would certainly not be enough for "self-cleaning" through continued oil leakage!
Look up "AGR" and "intake manifold," then you'll understand what I mean.
haithamina
P.S. It seems that Ulf's and my posts overlapped just now...

In the Passat, only automatic transmissions were available . Mostly, it was the 'larger' ones like the AVF with a 5-speed Tiptronic.

I'm familiar with the problem of a clogged intake manifold. I had it on my Golf 4 AJM engine two years ago. I even removed the entire manifold, cleaned it (it was slightly clogged), but it didn't solve anything.

"Tonight, I'll check if I have an AGR cooling system. I'll measure the vacuum pressure in different locations again (if I can find a pressure gauge or something similar), and if my old laptop battery can last for at least fifteen minutes, I'll do another test drive."

Please check if the electric pre-feed pump (in the tank) is still working. When the engine is running (at idle), a significant overpressure should be measurable at the fuel pressure sensor.
If the VFP fails, it can cause a traffic jam, and this may lead to supply chain disruptions.

Reveal the secret of the mileage!
haithamina

Oh, I see. Sorry.

He actually only has "just" 167,000 km on it. We've had the car for about 10,000 km. It's actually been running really well, but I only noticed that since I drove a different car with 101 horsepower. The vehicle has always been serviced according to VW's maintenance schedule, which unfortunately doesn't necessarily mean anything...

Possibly, the other one might not be a standard production model either! The 101 horsepower engine is extremely sluggish in that heavy car. When this engine is tuned, it feels much more agile, so that can be misleading.

You're right!
"101 horsepower for a 1.6-ton vehicle isn't much. According to Volkswagen, it takes 12.9 seconds to reach 100 km/h (62 mph)."
So, the 170 horsepower DSG version that I recently drove felt quite different .
haithamina