Timing belt replacement: Adjust timing and test

hello,

After the timing belt was replaced on my T4 at the workshop, I reset the boost pressure start value using VAG-COM.
I noticed that the fluctuations in the FB value vary by approximately +/- 7 units.
I was only able to estimate the optimal value.
Other effects include:
- Large area within which the tensioning roller moves (the indicator wobbles).
- When accelerating in the lower RPM range with approximately 25% throttle, the engine "vibrates" at a frequency similar to the rotational speed of the ESP's timing belt.

I hope this is explained clearly!

My initial approach was that the timing belt might not have been manufactured correctly.
That means that the teeth don't always have the same spacing.
and thus, the timing belt changes the distance between the gears.

Is that possible, or does the problem have a different cause?

best regards, leo

Hi.

Could the timing chain have suffered damage due to prolonged storage?
Does the TDI engine have a tensioner pulley on the ESP (electric steering pump) side? (I'm only familiar with the 2.4 naturally aspirated diesel, which doesn't have a tensioner pulley there.)
Is the tensioner new?
Did you also replace the other belt (the crankshaft side)?

I don't think it's about the belt being too loose; rather, it's more like it's "stiff" – meaning that a portion of the belt doesn't bend as easily around the pulleys as the rest of it does.

m;

hi,
As far as I can tell, the ZR was active on the ESP.
And yes, the Z-ray sensor on the KW side was also replaced.
The arrangement of the Zylinderkopf-Entlüftungssystem (ZR-ESP) is similar to that of the ACV (102 hp) engine, featuring a tensioner roller and an eccentric roller.

What I forgot to mention is that I replaced the tension spring, but it didn't improve anything.
And I have checked the eccentricity to ensure it is running smoothly, as much as possible.

best regards, leo

dieselmartin wrote:

Hi Could the timing chain have suffered damage due to prolonged storage? Does the TDI engine have a tensioner pulley on the ESP (electric steering pump) side? (I'm only familiar with the 2.4 naturally aspirated diesel, which doesn't have a tensioner pulley there.) Is the tensioner pulley new? Did you also replace the other belt (crankshaft side)? I don't think it's about the belt being too loose; rather, it's more like it's "stiff" – meaning that a portion of the belt doesn't bend as easily around the pulleys as the rest of it does. m;

hi martin,
What influence could the other timing belt have?

best regards, leo

@dieselmartin:
What effect could changing the timing chain on the crankshaft side have now?

best regards, leo

Hello Leo!

Are you sure that the control of the injection start was performed in the DEFAULT SETTINGS MODE? If not, then the constant fluctuation can be explained by the regulation activity of the pump/control module.
Unfortunately, there are still enough "experts" in workshops who don't understand the difference between the basic setting mode and the "normal" mode.

Regards,
Alex.

Hi Leo,

I was practically offline all weekend, so I'm just getting to this now.

"Spritzbeginn" refers to a relationship or correlation between the crankshaft position and the injection timing.

For the R4 TDI, only the position of the pump is crucial.
On the R5, all the inaccuracies from KW (front) to NW (rear) are transmitted via the right and left tensioners to the pump. This means that if you install the right (KW) belt incorrectly or if it's damaged, the pump will also malfunction.

I just wanted to point out that there are significantly more factors and inaccuracies (compared to the R4).

m;

hi,
@donalexo:
Since I personally configured the firewall and I made sure to understand it thoroughly, I can rule out an error on my part.
@dieselmartin:
Therefore, the vibration damper and the kilowatt-hour (kWh) meter could also be a cause of the fluctuations, or it could be a combination of all these factors.

Here's my question regarding this: Is it normal for the ESP-ZR to fluctuate?
And if so, how much is it allowed to be?

Otherwise, the engine runs better than before!
topspeed is fine again after several hundred kilometers of full throttle; it's very okay. (up to 170 km/h with 88 horsepower, a pretty powerful car) .
in the city, there is now less accelerator pedal pressure at the same speed.
and furthermore, it seems to consume less.

best regards, leo

If the vibration damper is causing vibrations instead of dampening them, it may be the culprit.

The damper only drives the ribbed belt, and has nothing to do with the timing belt (ZR).

The engine should even run without the S-damper (the water pump runs via the timing chain, so it will continue to run even when the battery is dead ).

m;