Jerking/Vibration at 1800 RPM (ARL TDI)

Hey everyone,

Let's briefly go over the background. At just under 90,000 km, the timing belt broke, and the engine seized at the same time http://www.duckyboys.net/smilies/geschockt/blink.gif.

So far, so bad. VW then installed a new engine under warranty. However, I now have the problem that at approximately 1750-1800 RPM in EVERY gear, the entire car experiences a noticeable shaking or vibration at a relatively high frequency. It feels like someone is constantly shaking the driver's seat. The frequency of the jolting is the same in each gear, meaning it's consistent across all speed ranges.

First, the drive shafts were inspected and removed in the workshop; they apparently weren't the problem. Then, the entire front suspension was detached on the lift, and the engine was started to potentially release any tension caused by the engine replacement -> no improvement.

Then the mechanic was ready to install a new engine, or at least just the engine block. However, he wanted to replace the pump nozzles first, because they hadn't been changed after the timing belt failure. And there you go, the jerking was gone – unfortunately, only for a very short time! Perhaps it had simply become more difficult to reach that specific RPM where the phenomenon occurred. Anyway, it's fully back now (10,000 km after replacing the PD elements).

Now I was back at the workshop, and the master mechanic was quite puzzled as to what else could be the cause. According to his reasoning, it can't be a problem with the engine anymore, because the issue was temporarily resolved by installing the new PD injectors.

After installing the new PD elements, of course, the valve cover gasket blew out (when things go wrong, they really go wrong...).

A trusted mechanic had suggested a few months ago that I should have the cylinder head checked for hairline cracks, because he had encountered a similar issue himself and had spent a lot of time and effort trying to figure it out. VW, however, does not believe that .
Could it also be that the work done on the valve cover caused the cylinder head to become strained again, temporarily sealing the hairline crack? They may have tightened the head screws.

Please share your thoughts on what might be causing this. It probably isn't related to the suspension, because it occurs in every speed range, but only at a very specific engine RPM. Oh yeah, back then, the wheels were also swapped out for testing... but it didn't make any difference :rolleyes:

The engine is a 150 horsepower diesel, with the engine code ARL. Of course, there's nothing in the error memory; it would be too easy.

Thank you very much for reading so much text .

Christian

Hi.

I can only offer "speculations":

They also had a friend who had two PD elements replaced by VW because they were reporting "strange values" – but it turned out to be the dual-mass flywheel.

That was a 100 horsepower PD Bora.

I'm not sure how it relates to your problem, though.

m;

Try deactivating the EGR valve. It has led to success in various cases.

Try disabling the AGR (Abgasrückführung). It has led to success in various cases...

It's not the AGR's fault .

Hmm, a dual-mass flywheel is certainly another candidate, although that wouldn't explain why the phenomenon completely disappeared for a short period . By 'short period,' I mean only about 1000 km.

What makes you so confident about the AGR (Abgasrückführung)? Did you also seal it properly with a metal plate, as it should be? That's what brought me success... (It's just an AWX engine, but...)

joergs wrote:

How does the agr make you so secure? Did you also, as it should be, seal it with a metal plate? That's what brought me success... (It's just an AWX, but...)

Hi Jörg,

That's interesting... Based on what criteria or observations did you measure the success?

What "unsuccessful" approaches did you try before using the sheet metal?

Did the valve not close properly without vacuum? If so, how old was the car at that time, and what was its mileage?

How does the agr make you so secure? Did you also, as it should be, seal it with a metal plate? That's what brought me success... (It's just an AWX, but...)

Okay, so I only tried it myself by disconnecting the vacuum hose. However, the workshop also deactivated the EGR system, and if I remember correctly, they tried doing that by sealing it with a metal plate. I will bring it up with her again.

How does the agr make you so confident? Did you also, as it should be, seal it with a metal plate? That's what brought me success... (It's just an AWX, but...).
Hi Jörg,

That's interesting... Based on what criteria or observations did you measure the success?

What 'unsuccessful' approaches did you try before using the sheet metal?

Did the valve not close properly without vacuum? If so, how old was the car at that time / what was the mileage?

Between 1600 and 1900 RPM (the AWX engine builds boost pressure and delivers torque earlier than the ASZ), there were some significant jolts, and then it settled down...
Removing the hose didn't help. When the EGR valve was blocked with a piece of metal, the jerking also disappeared. The cause was a clogged EGR valve that was apparently not closing properly.
That was approximately at 130,000 kilometers.

What makes you so confident about the agr? Did you also, as it should be, seal it with a metal sheet? That's what brought me success... (It's just an AWX, but...).
Hi Jörg,

That's interesting... Based on what criteria or observations did you measure the success?

What 'unsuccessful' approaches did you try before using the sheet metal?

Did the valve not close properly without vacuum? If so, how old was the car at that time / what was the mileage?

Between 1600 and 1900 RPM (the AWX engine builds boost pressure and delivers torque earlier than the ASZ), there were some significant jolts, and then it settled down...
Removing the hose didn't help. When the EGR valve was blocked with a piece of metal, the jerking also disappeared. The cause was a clogged EGR valve that was apparently not closing properly.
That was approximately at 130,000 km.

Hi Jörg,

Is the AGR (Abgasrückführung) system even considered at 1800 RPM and during constant speed driving, meaning no acceleration, just maintaining a constant speed? Because the AGR is already active in that case.

Best regards,