PD Rejection: Shocking Results Revealed

Hello,

Just now, for the first time, I had to drive my Polo onto a sidewalk, at almost a right angle, as is required.

The right front wheel was already off the ground, but when I tried to get the left wheel up as well, with a bit of momentum, there was a loud, hard thud that resonated through the entire vehicle.
At first, I thought I might have accidentally bumped into something, like a footstool.

After the shock, I realized that the engine was off. I restarted it and, with a little more gas, drove onto the sidewalk.

After that, I couldn't find anything else unusual. As far as I can tell without a pit or lift, everything seems to be in order underneath the car as well.

I can only explain the loud noise I heard as being caused by the engine stalling.

I'm used to the AFN having more noise than the gasoline engine... but such a strong, dry knocking sound . Is that normal for PD engines ?

Right now, I'm genuinely afraid that I might intentionally choke the little one at some point, just to explore it further .

Something inside me thinks things like, "At the very latest, after the 5th time of stalling, at least one engine mount will break and/or the timing belt will snap... "

Hi Ulf,

You are doing experiments .

I could imagine the following:

Normally, the car is intentionally parked, and the parking flap prevents it from swinging outwards.

If you stall it, the A-valve probably won't close quickly enough to gently force it to its knees , so the engine likely completed its last cycle with a large amount of fuel injection, and then possibly hit somewhere it would never have reached with the valve closed.

Where does the engine move when you deactivate the flap?

Perhaps it's not aligned correctly, just like your camshaft.

Greetings.
m;

dieselmartin wrote:

You are doing experiments

.
... but this wasn't intentional!

Quote:

Where does the engine move to when you deactivate the flap ???

I haven't tried it yet. But without fuel injection, a PD (presumably referring to a specific type of engine) would behave similarly to a VP engine (another type of engine) when it stalls.
And as I recall (IIRC), it was previously reported here that it vibrates a bit more, but doesn't make any loud noises.

Quote:

Maybe it's not aligned correctly, just like your camshaft!

I actually don't think so... I've already checked almost everything in the engine compartment, and nothing about the suspension looks crooked or improperly mounted.

The behavior during driving also seems completely normal to me (no loud noises, noticeable fluctuations in load, etc.).

I experienced the exact same issue with my 130hp PD A4 the other day.
It made a bang, as if the entire engine had ripped off .

In my region, PD models are actually quite frequently used as driving school cars. If components started failing after only 10 attempts, you would hardly see any VW cars being used as driving school vehicles anymore.

So, don't worry too much, and if you do, you still have a warranty (sorry, at VW it's called a guarantee).

Best regards, D.

Hi!
Okay, now it's my turn to chime in. So, I've never heard of trying to start a car by revving the engine like that. However, I once tried to start a warmed-up engine by rolling it down a hill. At the time, I thought the engine was going to give out. I definitely wouldn't do that again voluntarily...

Best regards,
Dirk.

Hi,
The Passat PD models in our company stop working with the slightest attempt to shut them off. Perhaps it's a safety function of the EDC (Electronic Diesel Control) system?

During the initial break-in period, I occasionally stalled my ASZ engine when starting. It would always shut off "quietly" and smoothly. Once, however, after a switch in a hectic...
Urban chaos and street fighting (the first one should have been, it was the third, at least... ) also had a similar impact, like a blow from the engine.
It seems to me that it either occurs randomly from time to time, or depending on the engine's speed or operating condition. I haven't wanted to conduct any further experiments yet...

@ ulf:

Here's an idea: If you abruptly shut off the engine, not gradually, it could happen at a point where fuel is being injected and ignited in a cylinder. If the engine then suddenly reverses its direction due to external influences after this abrupt shutdown, it would have to force the exhaust gases out through the intake valves. If that exhaust is highly compressed, I can imagine it making quite a loud noise. After all, the intake area doesn't have any sound dampeners designed for such extreme situations. Hopefully, the pressure wave won't cause anything to crack or break.

Greetings.

Eike.

eike wrote:

. . . where fuel is injected and ignited within a cylinder. If the engine, after being abruptly shut down by external factors, suddenly reverses its direction of rotation, it would have to expel the exhaust gases through the intake valves. If that exhaust is highly compressed, I can imagine that it would make quite a loud noise. After all, the intake area doesn't have any mufflers designed for such extreme situations. Hopefully, the pressure wave hasn't caused anything to crack...

Hi Eike,

I don't believe that happened.
Neither a misfire (the running behavior, engine noises, power, and fuel consumption are completely normal), nor a "backfire," because the sound clearly felt like a mechanical collision, but not like a huge explosion.

I've found some small crumbs of a white substance on the longitudinal member, near the engine mounting point on the transmission side. This substance definitely wasn't there before.
It might be something about the color on many of the screw heads (for whatever reason...).

Then, for example, a screw head on the motor side of the rubber mount could have been crushed against a part of the bodywork due to an extreme movement of the motor, which would also explain the type of noise.

So far, I haven't been able to see anything white-painted in this area without having to look around corners using a mirror. However, I will try to find some.

I will only look inside when larger parts are hanging out .

Hi,

I don't think the behavior described by Ulf is typical for a PD (Piezo Injector) system. I once accidentally aborted the ASV (Automatic Stop-Start Valve) process early on in my first TDI car, when I was in a hurry, and that also caused a fairly strong jolt similar to what was described. Later, I also experienced what Joegolf wrote about, which is that the engine started in 3rd gear instead of 1st, and with a relatively hard engagement, but in that case, there was no jolt. I think there's definitely something to Eike's theory about the timing between the injection and the abort time.

Best regards,

Jan.

Jan6K wrote:

I think there's definitely something to Eike's theory about the timing between the injection and the exhaust stroke.

Hi Jan,

if it were possible to derive the "wobble amplitude" strength of the motor-gearbox unit from that, I would agree with you .

I once used a shard of glass to search the area with the white crumbs for screw heads, but I didn't find anything where they might have fallen off .

It's possible that the impact also came from the suspension on the drive side.
However, in the Polo, everything is so gloriously complex and intertwined due to space constraints that I haven't felt like spending half an hour disassembling parts just to be able to examine the suspension from all angles.

Okay, Ulf, just so you know: engines like the 3.0i gasoline engine also produce similar vibrations.

otherwise: automatic is awesome http://www.cheesebuerger.de/smilies/frech/2.gif


CU Gremlin.

Gremlin wrote:

so, Ulf, if it makes you feel better: engines like the 3.0i gasoline engine also produce such vibrations...

Well, what's this, no TDI-specific stuff... how mundane .

Quote:

otherwise: automatic is awesome

Not for me.
Dear ~ It's better to have a sudden, unexpected issue about 3 times a year than to be cheated by some software during a critical process like a system upgrade. With a DZR (Direct Drive System), you can only achieve results through trickery and manipulation, and you'll also experience increased weight and higher consumption, and so on.

Speaking of automatic transmissions: I once had a rather crazy idea about how to build a continuously variable, slip-free, and low-loss acceleration gearbox.

You all remember those good old audio cassettes. When you fast-forwarded on a Walkman, the drive spool would initially spin very quickly relative to the take-up spool. The ratio would constantly change until the take-up spool was spinning incredibly fast.

If one were to manufacture such a winding band drive from high-strength steel tape or fiber-reinforced special tape, one would have the ultimate acceleration transmission. It would be very efficient and stepless. But unfortunately, it would suffer from spontaneous band breakage, where the end of the tape would have to be discarded (like in old tape recorders, who still remembers those?).

Disadvantage: The translation speed is fixed and can only be optimized for a specific engine characteristic curve, vehicle mass, and rolling resistance.

Otherwise, it would be impressive. You could leave a Porsche standing with a housewife's Corsa.

I hope that wasn't too off-topic.

Perhaps my wrap-around gearbox will be featured in various acceleration races soon.