Vibration at Acceleration: Causes & Fixes (Solution)

Interesting new problems seemed to be plaguing me and my Audi A4 B6 1.9 AVF.

A few days ago, I had a minor issue where the car stalled because I drove through quite deep water. After draining the water from the engine compartment and drying everything out, I managed to get the car running again.

After a few days, I suddenly noticed a slight vibration when accelerating. Two days later, the vibration became so severe that it was difficult to maneuver the vehicle.
I immediately suspected the drivetrain because I didn't notice anything when I took my foot off the gas pedal, nor when I pressed the clutch.

I can rule out a dual-mass flywheel because I replaced it with a single-mass flywheel three years ago: VALEO 4KKIT.
Now that I'm home, I inspected the driveshaft on the driver's side and was shocked to find that the boot of the inner joint is damaged.
After that, I removed the drive shaft and flushed out the bearing... There was a lot of dirt inside.
I checked the part and couldn't find any major issues... However, I immediately ordered a new driveshaft because on my car model, you can't replace the inner joint separately.

Okay, so now the question is: Could these vibrations be coming from somewhere else?
The VA suspension is completely new.
Wheel bearings as well.
Can this be caused by PD elements?

Quote:

Can this be caused by PD elements?!?

No, it doesn't happen when reversing and accelerating.
Because when reversing, the joints on the relatively unused side are put under stress...

Okay. Thank you, good point!
I'll test it once the drive unit arrives to see if this issue also occurs when driving in reverse.

I thought that perhaps a fuel injector might have been damaged by the water.

Well, if the car has sucked in water and even a small amount of it got into the combustion chamber, quite a few things can break.

Kitwing wrote:

...After I had a minor issue a few days ago where the car stalled because I drove through quite deep water, I managed to get it running again after draining the water from the engine and letting everything dry out.

Then you must have driven through water that was almost as deep as the hood, or your air intake is located in a very unfavorable position in the engine compartment/fender?!
If you had water in the engine oil (LLK), and there are no holes in the intake manifold large enough for a finger to fit through, then it's likely that water was also sucked into the engine, and as Matthias said, that's very damaging to the motor.
I'm not so much thinking about the timing chain in this case, but more about things like connecting rods and valves, or even the crankshaft.
haithamina

Quote:

If you had water in the coolant reservoir, without any finger-sized holes in the intake manifold, then it's likely that water was sucked in, and as Matthias said, that's quite damaging for the engine.

Oops, I completely missed the romance part.

The air intake is located behind the radiator grille, directly beneath the hood.
Is there still an air filter present? In the event of a water leak, quite a few things can happen, as mentioned before.

However, we first need more input. And please, no lengthy essays.

A bent connecting rod or a defective connecting rod bearing should almost certainly be detectable through the idle speed control system.

I have already replaced the filters.
After drying, it ran a bit strangely for the first few kilometers, but then went back to normal as before. (Air filter replaced/mass airflow sensor cleaned, and checked with VCDS).
For four days, everything went smoothly.
Drove 120 km every day.

As I said, it runs perfectly fine when idling. Also, there was no water visible in the oil.

The water level was approximately 15 cm high. Nevertheless, it absorbed some moisture because there was water in the liquid cooling system.

And shouldn't a water leak be ruled out if I was able to drive for four days without any problems?

Hi Kit!

At a water depth of 15 cm, it should also be possible to rule out the presence of water in the cooling system .

Please provide a brief log of the performance characteristics (MWB) for units 13, 18, and 23, both in cold and hot conditions, while idling.
Then a water feature should be ruled out for now... or maybe not.

Best regards from Munich!

Okay, I'll do it as soon as I get home!
Thank you for your help.

PS: The water was definitely in the intake manifold; I had removed the hoses for inspection before starting it, and some water came out. Both the air filter and the mass airflow sensor were also wet.

Attached is the log file from a cold start.

and while it's still in a somewhat warm state. Let it run for 15 minutes because the drive shaft hasn't arrived yet.

Hi Kit!

After a preliminary review of your logs, I see no significant issues other than a slight weakness in cylinder 2 at the beginning of the cold start log.

Perhaps the dirt was pushed deeper into the joint by a defective seal on the inner bearing, which is why you're experiencing vibrations.
Okay, first things first, we need to replace the driveshaft.

What I still don't quite understand is whether the water remains in the closed-loop cooling system.
What is the approximate volume we're dealing with here? Is it 1 liter, or just 10 milliliters?

Best regards from Munich!

Thank you for your effort.
Okay, it's hard to say exactly how much coolant ended up in the engine oil... but I would estimate around 200ml total. However, since I drove through the water without giving it much gas (or couldn't have), it probably didn't get very high towards the intake manifold.
The water was a mixture of oil and water.
As a result of this, I completely cleaned the intake manifold.
I think I got lucky again, more than anything else.

Theoretically, condensation could also be present in the coolant system, but 200 ml is a significant amount.
It's quite an achievement to suck in 200 ml of water through the "near-water injection" system using the turbocharger and store it in the intercooler.
Everything is a bit strange, and it's also odd that the turbo apparently isn't causing any problems?
haithamina

I thought the same thing, so I disassembled and cleaned the intake hoses all the way to the turbo, and I checked the shaft play. It seemed pretty good, with almost no axial play.
After that, I checked the valve timing gear (VTG), which was extremely stiff, so I fiddled with it until it became reasonably easy to turn.

After cleaning and reassembly, it ran... poorly at first, but that improved after about 25 kilometers of driving.
I hope the driveshaft arrives today so I can continue testing and figure out where the external vibrations are coming from.