Jerky Acceleration: Causes & Fixes

Hello,

Since I already described my problem in the general technical forum and haven't received any answers yet, I'm trying again here.

I have at my...

1999 Audi A4 Avant with AFN engine and approximately 140,000 km.

The following problem:

"When accelerating, I experience a slight jerking or wavy acceleration between 1600-2000 RPM in the 3rd and 4th gears. In the lower gears, I notice nothing, and only very slightly in 5th gear. I also don't notice anything in the other RPM ranges. Strangely, this jerking is more pronounced when using partial throttle than when pressing the gas pedal all the way down. When you fully depress the gas pedal, you only notice it very slightly."

Here's what I've done so far.

-Error codes read, none found.

-MAF sensor cleaned. My predecessor installed a Pierburg MAF sensor, which I believe was originally a Bosch unit. It has been in the car for approximately 70,000 km.

- The VTG linkage was checked for smooth operation, but I need to mention that I had a vacuum hose connected to the actuator, which was constantly under vacuum. It moved about 90% of the way with the same speed, but the last part was a little slower. However, the movement was smooth and without any jerking.
I repeated that approximately 100 times.

- I also noticed that the vacuum reservoir seems a bit loose after the solenoid valve, but I'm not sure if that makes a difference.

-Solenoid valve controlled via VAG-COM -> The VTG linkage moved up and down.

-Air filter cleaned.

My car probably has a dual-mass flywheel, and it could potentially be the cause of the problem.

The car is mainly driven on country roads, covering approximately 55 kilometers per day.

AGR is ready.

Can anyone give me a tip on what else I can do to fix the error?


Regards,

Thomas.

thom wrote:

.... Can anyone give me a tip on what else I can do to fix the error?

Use the search function

There are probably the most posts about troubleshooting VP TDIs.


Started:
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Hello,

I've read a few posts about the jerking or wavy acceleration.

However, I'm not experiencing any idling issues, and the MSG (presumably a system or component) is not going into emergency mode.
Of course, it's possible that the MSW (Multi-Station Workstation) might not operate as smoothly as when it's new, but I don't want to disassemble it just yet.

Can I log any measurement data to rule out that possibility?
Are there any tables available where I can compare this information, or can I post it online and you can take a look?

Regards,

Thomas.

thom wrote:

AGR is to.

Is it also 100% certain? How did you achieve that? Did you just remove the hose, or did you put a plate in between?

Plate in between.

Hi there,

I'm just here for a quick moment and I've just skimmed through this thread.

Take a look at this: /viewtopic.php?t=6529

Perhaps this will help you.

Best regards,
Wool.

It might sound silly and trivial, but we once had a similar case... we ruled out everything else until we realized that two rims had a slight deformation. This only occurred under specific load conditions.

To completely rule out the mass airflow sensor.

a) Try a new LMM (if a diagnosis is not possible) or/and...
b) Diode trick (works forever) Caution: NOT approved by TÜV (German technical inspection agency)!!! ---BE (brightness) will turn off!
(Using 5 volts on the MAF sensor with a 1N4148 or 1N4001 diode connected in the forward direction to the measurement input works without problems for many AFN engines. This fools the engine control unit into believing that the maximum possible air mass is present, which in turn allows the engine control unit to release the maximum permissible fuel injection amount according to the fuel map.)

So, can you be 100% certain that your EGR valve is sealing properly? Otherwise, I would suspect a stuck EGR valve. It's not activated at full load.
Here's another idea: You've sealed the AGR with a metal plate, but is the vacuum diaphragm of the AGR still airtight? Is the vacuum hose connected to the AGR okay? Or was the entire control valve already disconnected beforehand?

So, the AGR is locked in this way.
There are plates made of aluminum installed before and after the AGR (Abgasrückführung - exhaust gas recirculation) valve, specifically where the seals are located. The AGR valve is still being activated. However, I think these two plates should be sealing properly.
Unfortunately, I haven't had time this week to create a log.

Best regards,

I also used to use aluminum. It's not a good idea. It will eventually crumble. I'm not sure if it's due to the heat or the aggressive components in the exhaust fumes, but it definitely doesn't last.

Best regards, Rainer.

Sure, ST37 or stainless steel works great. Aluminum is definitely not suitable.

Today, I removed the two aluminum plates, and I was right – the first one was already slightly corroded.

I need to make some from stainless steel.

Today, I logged data from measurement blocks 0008 and 0011.
Can someone tell me if these values seem reasonable?


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