ATD: Engine Jerking at 1000-1500 RPM

Hello,

"Especially when driving through towns or behind trucks, when the engine speed in 5th gear drops below 1500 RPM and a constant, slightly reduced speed (1000-1500 RPM) is maintained, I experience a slight jerking in my ATD. If you then release the accelerator (engine braking), or lightly press the accelerator, the jerking disappears immediately, and you can accelerate smoothly from idle speed."

In the fourth gear, the jolting is also present, but not as noticeable.


Regarding the car (Fabia TDI, 74kW, ATD).
96,000 km
AGR sheet metal (intake passages visually clean).
Coolant temperature sensor in the diesel line.
Timing belt tensioner/valve timing was mechanically checked and adjusted approximately 2 weeks ago (new at 81,000 km).
All filters are approximately 15,000 km old.
Oil (50601) has been in the engine since the end of January, and I've driven 15,000 km since then.

The engine has been running rough since I bought the car (approximately 15,000 km ago). Initially, the dealer mistakenly used the wrong oil, 50500 10W40, during the "service," but it was later changed to the correct 50601 oil after about 1,000 km.

A phone call with the previous owner didn't yield a solution – he hadn't noticed the stuttering.

Otherwise, the car runs perfectly fine, starts on the first try, and idles smoothly. The power is also good, with 4250 RPM in 5th gear; the dynamometer reading confirms 114 horsepower. However, the engine noise becomes a bit louder at RPMs above 4000.

Could any of the PD (piezo injector) elements have been damaged by using the wrong oil initially (approximately 1200 km, including full load)? If so, how can this be checked?
Does the EGR sampling rate still play a role when the EGR system is defective?

I have a 1-year warranty (starting January 2004) from the dealer (independent) on the engine and transmission. However, I don't want to hand over the car without clear instructions, as I've already had enough trouble with the oil issue...

Hi,

Unevenly working PD elements can certainly cause such jolting effects, but it's probably a bit too early to attribute it to that.

What does the idle speed control system say?

Bertil wrote:

Hi, Unevenly working PD elements can certainly cause such jolting effects, but it's probably a bit too early to conclude that's the cause. What does the idle speed control say?

Without an OBD2 adapter, I can say as much about measurement group 13 as I can about the weather next week...

I vaguely remember seeing the values during a check-up at the doctor's office – I believe they were all optimal. However, I'm not 100% certain about that.

Could it be possible that one of the vehicles picked up some of the unauthorized oil from the operator? I drive past a BOSCH Service Point (Diesel Service) every day – would that perhaps be a way to get some clarity?

Alternative thoughts?

I will take a closer look at LLRR at some point.