Engine Misfire: Grey Smoke Explained

Hello everyone,
I'm new to this forum. I'm 47 years old and learned the trade of automotive mechanic almost 30 years ago. I have a preference for VW Caddys. I had a VW Caddy 14d for many years, and I was very satisfied with its reliability. About a year ago, I bought another Caddy, specifically the 9kv model, but I'm at the end of my knowledge . I hope someone here can help me.
Regarding my car:
VW Caddy, manufactured in 2003, with a 1.9 SDI engine producing 64 horsepower. Engine code: AYQ. Mileage: 124,000 km (according to the odometer).
What new engine technologies were introduced?
Cylinder head gasket and seals (all gaskets in the cylinder head area).
The EGR valve is new, and the crankshaft ventilation system has been replaced.
The new glow plugs and fuel injectors were sent for regeneration. The throttle valve and temperature sensor are new.
Regarding my problem:
The Caddy is producing too much white-gray smoke. It's sputtering and puffing out the smoke. Sometimes it seems like it's choking, then it starts running again. I disconnected the throttle body connector, and the engine runs smoothly without sputtering. However, it still produces smoke under load. Then I reconnected the throttle body connector and also disconnected the temperature sensor connector in the air filter housing. Again, the engine runs normally, but the smoke appears under load.
I've now received the VCDS device, but it's not showing any error codes. I'm at a loss and don't know what to do next.
Does anyone have any advice for me?

I am very grateful for all the answers.
Best regards,
Marek.

Welcome!

Okay, here's the translation:

Now, in order:

Why and for what reasons were the respective repairs carried out?
2. Are the fluid levels (oil or water) decreasing?
"Even if no errors are stored, please include an Autoscan so that we have more information."

It was an impulse purchase.
After a few days, it started emitting a very acidic, pungent smell from the exhaust. I thought the valve stem seals might be worn out, so I decided to replace all the gaskets. The intake manifold was full of black, tar-like residue, which seemed strange to me; I suspected someone had been using plant-based oil. I haven't driven the car much because people behind me were honking their horns due to the smell.
I'm at work now and can only attach a photo of the car scan.
There's an error listed, specifically the plug that needs to be disconnected in order for the vehicle to operate. When the plug is connected, there are no errors.
If anything else is needed, I can rescan the document tomorrow morning.
Best regards,
Marek.

Valve timing is correct, crankshaft pulley seat has been checked for tightness, keyword: kill switch screw.

Good morning.
I had it checked out over the weekend. There was no play on the crankshaft pulley, and the marking was also correct. He also checked the pump, and the start-up performance was fine.
What else could it be?
Best regards, Marek.

Hi there,
"White smoke always indicates unburned diesel fuel. The causes can be a misaligned injection timing or leaking injectors."
Black smoke indicates that there is insufficient air for the injected fuel. Possible causes include: a clogged intake path and/or air filter restricting airflow, an open exhaust gas recirculation (EGR) system, low compression, incorrect fuel injection timing, etc.

First of all, the intake manifold and the channels in the cylinder head must be thoroughly clean. This applies regardless of whether you're dealing with white or black smoke. Were both of these things done?
Then adjust the valve timing. If this was done professionally by someone else, I don't understand why the problem isn't being resolved. To determine the start of injection, please post a picture of the TDI graph here.
What are the compression values?
What were the results of the tests performed on the injectors after they were refurbished? What is their condition now?
A faulty nozzle can be identified through the idle speed control system.
hg
Herbert.

Hello,
Does the display above the odometer still show "total"?
Not that the car actually has 4,240,000 kilometers on it, and the engine and fuel injection pump are simply worn out.

Best regards,
Sören

4,240,000 km? 4,240,000?
That would be .
hg
Herbert.

It should naturally be 424,000 km .

Where was the timing (or crankshaft position) checked, specifically at the crankshaft pulley?

Was ist passiert mit the crankshaft pulley? If it hasn't been removed, we won't be able to check the tightness of the fit.

So many questions, I'll try to answer them all.
The Caddy was checked at a friend's "after-work workshop," and they said everything seemed to be fine.
I have certain questionable feelings .
I'm still looking for someone who is knowledgeable and can take another look at it, preferably considering my absence . Or is there anyone nearby (zip code 58840) who could take a look?

Yes, I cleaned the intake manifold and all those parts myself about four months ago.

I think the vehicle's suspension is well-designed.

The mileage reading on the odometer is almost accurate.
Best regards,
Marek
The injectors were sent to Biberach for regeneration. The letter simply stated that they were finished and included the price (approximately €280).

Hi there,
The compression could be more even, but it's still good. Have the channels in the cylinder head been cleaned?

You can check the idle speed (both cold and warm) and the fuel injection yourself using VCDS. There should also be measuring blocks and a timing checker specific to the AYQ engine available.
I would only test the worm gear initially with the lever attached and the wheels blocked. Otherwise, you might open up another can of worms.

Quote:

The injectors were sent to Biberach for regeneration; the letter only stated that they were finished and the price (approximately 280 euros).

What exactly does "regeneration" entail in this context, and what should be included in that price?
hg
Herbert.

"Addendum" or "Postscript."
"The injectors are delivered with test reports and can be reinstalled into the vehicle."
I have also read the reviews on webwiki.de/diesel-technik-biberach.de.

The compression is excellent, and the cylinder deviations are negligible.

There are essentially only two approaches: either thoroughly check if the valve timings are correct, and not just do it after work hours.

Specifically, check the oil pressure sensor on the crankshaft, install a pressure gauge at the VP37 port, and use a ruler to measure the camshaft (the valve cover needs to be removed for this). If everything is good after these checks, proceed as before; otherwise, perform the same steps.

If the bottom cover is removed, check the hydraulic lifters and, above all, the camshaft for wear.

Is that completely okay? If so, the only remaining possibility for me is a mechanical fault with the VP37.

Thank you very much for the answers.
Okay, it's best to double-check the valve timing again. I'll see if I can check it myself using RÜDI's instructions, or if someone in my network can check it while I'm away.
I will get back to you here as soon as I make more progress.

I will try to adjust the idle speed using VCDS this weekend myself, as I have the software.

Thank you very much and best regards.

You can find all the repair manuals, including those for the Caddy, under https://erwin.volkswagen.de/erwin/performSearchArticle.do. This includes the manual titled "Diesel injection and preheating system with distributor pump."
It contains a compilation of all error messages from the MSG, the readable measurement data blocks, and the configuration settings.

With this information, it is also possible to meaningfully check the condition of the VEP and make a proper adjustment.

The flat rate for one hour is €8.33.
If you don't have a credit card, maybe a friend can help you out.

I'm also familiar with these documents from my old 1Z, but the values and possibly the data blocks might be different. The diagnostic process also works with the RLF (presumably a diagnostic tool) and VCDS (a vehicle diagnostics software).

hg
Herbert.