Polo 9N3, 1.4 TDI: Intermittent jerking/hesitation

Hello everyone!

Perhaps one of you can help me.
My reliable Polo 9N3 (1.4L TDI, BWB) has recently started to jerk or stutter briefly while driving. Also, the acceleration sometimes feels quite weak. I press the accelerator, and it only accelerates moderately, then – above a certain RPM – it loses power.

I have already replaced/updated some things (either for that reason or for another).
- Turbocharger pressure sensor.
- Air filter
- Fuel filter
- Oxygen sensor
- Air mass sensor.
- The DPF was cleaned.
- The maximum allowable leakage rate (LRR) is 0.50 mg/hour.

Can anyone give me a tip on what I should check or log?

Thank you very much!
Regards,
Volker.

Has the PD cable harness been replaced yet?

Rüdi wrote:

Wurde der PD Kabelbaum schon erneuert?

Hi Rudi,

No, not yet!
Is there a way to measure that somehow?
Or should I just buy a new one?

"Contact problems cannot be measured directly. I've encountered similar issues with PD TDI engines before. My first approach would be to replace it, as it's relatively easy to do and the price is in the low double digits."

Hi.

If it's not the PD cable harness but rather the throttle body/AGR valve, I would continue driving until a clear error code is logged. Because if these components are partially worn out and only sometimes malfunction, it can be difficult to diagnose without disassembling them.

Best regards, Rainer.

Hi!

Thank you for your suggestions!

I have obtained a wiring harness and will report back - however, not until after my return from vacation in September!

Hello everyone!

The PD cable harness was not responsible for the stuttering.
"Because of that, I now have an EGR valve error code in the diagnostic memory."

Quote:

Sunday, September 9, 2018, 10:04:30 PM: 25065 VCDS, a Windows-based VAG/VAS emulator, runs on Windows XP x86. VCDS version: RKS 18.2.1.0 Data as of: 20180313 DS287.1 http://shop.dieselschrauber.org/en Vehicle Identification Number: License Plate: A-VA 1101 Mileage: 426707 Repair order: "Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein perfekter Tag für einen Spaziergang." "Die Sonne scheint hell und warm. Die Vögel zwitschern fröhlich in den Bäumen. Ein leichter Wind weht durch das Gras. Es ist ein perfekter Tag für einen Spaziergang." Address 01: Engine Control Unit (ECU) File name: Control unit part number: Component and/or version: Encoding: Company number: VCID: 55A7B6FCAC60BFEC22-FFFE "One error found:" 001027 - Exhaust gas recirculation valve (N18). P0403 - 000 - Malfunction - Intermittent. Environmental conditions: Error status: 00100000 Error priority: 1. Error frequency: 1. Counter: 255 Time: 0. Environmental conditions: Speed: 0 RPM. Speed: 4.0 km/h Key press ratio: 0.0% Voltage: 12.69 V Air mass/Flow rate: 0.0 mg/H Key ratio: 21.3% Binary value: 00110000 Availability: Not available.

I think I'll get a new EGR valve and then let you know how it goes!

If you don't drive the vehicle every day, it would be a good idea to install, clean, and inspect the EGR valve and its components before buying replacement parts, to determine the exact cause of the problem. Does it have an EGR cooler? If so, inspect it carefully; it might be so clogged internally that it's not allowing sufficient airflow. Otherwise, cleaning is the next step... or, for the experienced mechanic, a replacement.
I would start by taking everything apart and seeing where the problem lies. This usually pays off when dealing with expensive replacement parts on older vehicles.

"In the 9N3 1.9 TDI engine I'm currently working on, the EGR valve and all related components were completely clogged with oil sludge/carbon deposits, with wall thicknesses in some areas exceeding 5mm."

I'm also familiar with that oil sludge from previous tinkering projects.

Unfortunately, the BWB also has an EGR cooler. However, everything located behind the engine is extremely difficult to access due to the small engine compartment.

Insofern möchte ich erst einmal mit einem gebrauchten Ersatz-AGR probieren, ob der Fehler dann verschwindet. I'm reporting!

Thank you all for your tips!

Hello everyone,

Here's a quick update after my garage cleanup today:
With the "new" (used) EGR valve, the Polo is running smoothly again!

Thank you all for your support!

Thank you for the feedback .

Hello everyone!

I probably got excited too soon.
The jerking stopped immediately after replacing the EGR valve. However, it now occurs intermittently again – although much less frequently and noticeably than before.

To make matters worse, a new phenomenon has emerged:
Sometimes, when idling, the engine runs unevenly, specifically with regular fluctuations in RPM that decrease. This is barely noticeable on the tachometer, but it's clearly audible and can be felt.

As far as I can tell, the idle speed control doesn't seem to be a cause for concern.

Cylinder 1: -0.47 mg/H
Cylinder 2: -0.40 mg/H.
Cylinder 3: 0.82 mg/hour.

The "sawing" sound only occurs when the engine is warm and doesn't appear until a few seconds after idling.

Do you have any other ideas about where the problem might be?

Thank you all!

Compare the target and actual air volume during sawing.

Best regards, Rainer.

dieselschrauber wrote:

Compare air mass setpoint/actual value during sawing? Best regards, Rainer

Okay, I'll check it out!
Thank you very much!

Interestingly, the saw no longer appears in the current version.

I will let you know as soon as there is any news!