1.9 PD-TDI ATD engine: hard shifting/jerking under load (Solution)

Hello,

My automatic transmission is acting up lately. After longer trips, when the engine is warm, the following symptoms are observed:

- When driving with light acceleration (10-20% pedal position) in the RPM range of 2500-3000, there is a sudden jerk when the accelerator is abruptly released or pressed.


Error memory is clear, otherwise no complaints, flawless operation, no jerking or stuttering, normal fuel consumption.

Do you have any ideas?

Are you perhaps referring to worn-out engine mounts? So that if the fuel supply is suddenly cut off, the powertrain will tilt?

Is the clutch switch reading plausible?

Engine mounts are likely not in the best condition after 270,000 km, but they seem okay after inspection and testing. The lower engine mount ("bone") connecting to the axle carrier is new.

Is the clutch switch showing up as defective or implausible in the error memory? Is that enough, or does it need to be checked properly using VCDS?

If so, in which accounting code will it be recorded?


Whatever the case may be:

- Cruise control is engaged, the engine is under load (slightly uphill), and when braking, which deactivates the cruise control, there's a noticeable jolt.

Hello,

You can check the measurement block 6 of the engine control unit; for details on the individual bits, please refer to the VCDS label file (click the blue link in the measurement blocks section at the top left).

Best regards, Rainer.

Hello Rainer,

Okay, thanks. I'll try it out later to see if it works properly.

checked.

All three pedal sensors (clutch pedal sensor, brake pedal sensor, brake light switch) are working perfectly. The accelerator pedal sensor also fits and, according to VCDS, regulates smoothly and without problems from 0-100%.

The jolt, however, remains. Do you have any more ideas?


I also read about LL-Ruheregelung.

- Cylinder 1: -0.78
- Cylinder 2: -0.12
- Cylinder 3: +0.10
- Cylinder 4: +0.79


As far as I can tell, it appears to be unremarkable, within the acceptable range, and the overall result is approximately zero. I initially suspected the PD cable harness, but should you really replace it just based on a hunch?

I can't imagine it's due to the PD cable harness, since the jerking you're experiencing only happens when you accelerate or release the throttle! I suspect there's too much play somewhere in the drivetrain. If you also ride a motorcycle: Does this sound familiar? When the chain is too loose, and you experience a jerk when accelerating or decelerating at low speeds, do you experience the same thing?
The old Mercedes exhibits a jerking motion when the Hardy disc is worn out.

Unfortunately, I'm not a biker.

Today, I removed the air filter housing and inspected the engine mount. There's about 5mm of play in every direction, as you can see in the markings on the photos. You can feel the play when you move it, and when you push it forward, the mount makes a noticeable creaking sound.

The Hardy discs could also be the problem at 270,000 km, but I think I'll replace the engine mount on the transmission side first. What do you think?

I would actually rule out a problem with the PD (power distribution). Another thing I've noticed is that the circuit sometimes hesitates under load, even though it's correctly configured (checked today). In my opinion, this suggests a seized engine due to a faulty bearing.

The question is, should I replace just one, or both of the upper ones? The one on the timing belt side is a bit tricky to remove, at least it was when I changed the timing belt.


Is this part already a hydraulic bearing from the factory? In any case, the replacement part from Lemförder is marked as a "hydraulic bearing."

Hmm, from a distance, I can't really tell if there's too much play. It's best to check the Hardy disc on a pit or lift. A pit would be ideal: One person in the car with the handbrake engaged, engaging and disengaging the clutch, moving forward and backward. You or someone who knows what they're doing should look and feel for any play! Even if the torque strut is new, it's worth checking. It's quite possible that there's excessive play in the drive shaft area, which could be causing the shifting to become jerky under load.
You could take a comparison vehicle from the VAG group with a PD engine, even without all-wheel drive, for comparison and compare the play in the drivetrain!

Yes, although I think that after 270,000 km, you can afford to replace the engine mount.

We checked the flywheel during the clutch replacement 20,000 km ago, and it was still in perfect condition. I will also check the torque support at the bottom.

I'm definitely going to replace the engine mount on the transmission side now. Or rather, I'll have it replaced, since I don't have an engine cradle.

You don't actually need a motor bridge; a jack or a sturdy bottle jack will work perfectly to protect the transmission! I even do it this way every time I change the timing belt.

Sure, I'm kind of hesitant to do it, because if the engine tips over, it will tip over .

Because with a motor bridge, I can set up the bearing in a way that's properly free from stress, which I don't think is as optimal when "pushing" it upwards from below.

Octavia_4x4 wrote:

Sure, I'm just not really brave enough to do that, because if the engine tips over, it will tip over

.

Laugh, that won't happen thanks to the torque support and the brackets on the timing chain side! Don't be afraid, it's easy! Even removing and installing transmissions WITHOUT a pit or lift, using a transfer jack! Bet you'll find it was easy, even after you've done it yourself?
Even when replacing the timing belt, I prefer the jack method because that awkward engine traverse gets in the way.

When completed - Box of Hefeweizen beer to me .

Yes, I almost have to try it .

How are you supporting the whole thing from below? Are you using a car jack and wood directly on the transmission? I don't want to break anything. Where would be the best place to start?

"Does anyone have the torque specifications for the engine mount? How do I install it without putting any stress on it?" Questions upon questions!


A case of beer is fine, but only if I'm really brave enough, and it works, and the error is then gone .

I was also a fan of the "hanging engine" method. However, since the preparation with my scaffolding takes a lot of time, a simple car jack and some wood will do the trick. For the DIY method, this is quite good, as long as you're not completely lacking in talent!