Old Problems, New Cause: 1Z Explained

The search results always only show 'KW screw'!!!

She definitely isn't the one!

A while ago, someone else had the same problem. See: Poor starting 1Z (not the KW screw). Unfortunately, it resolved itself.

Regarding the issue:

The vehicle occasionally starts up abruptly after being idle for an extended period (e.g., overnight) and sometimes has difficulty starting.

Sometimes it starts with a sputtering sound from the engine (about 3-4 seconds). Then it starts normally and produces a very small amount of white or gray smoke from the back.

Sometimes, it almost starts normally. Then, it doesn't run smoothly and turns off after about 1 second. This happens about three times, and then it runs normally.

Sometimes it starts normally (but this happens less and less frequently). When it's warm, it always starts 100%.

I did:

I replaced the KW screw about 20,000 km ago. I checked the torque yesterday.

The injection start time is perfectly fine (it couldn't be better).

The pump and filter are dry. There are no visible air bubbles in the line. Unfortunately, I haven't checked yet this morning.

Compression top (like new)!!!

The temperature sensor readings are also within the normal range.

During a dyno test, I noticed that the turbocharger is producing insufficient boost pressure. At idle, it's around 0.8 bar. Under full load, just before the rev limiter in third gear, it's about 1.2 bar. The air mass readings are also a bit low. Conclusion: The intercooler is leaking.

'But that probably won't have anything to do with the problem of it starting poorly, right?'

Otherwise, I haven't been able to identify any errors.

Okay, I'm a bit stuck here. When the problem occurs, the vehicle briefly emits white smoke, which I assume indicates unburned fuel, or does it?

If everything is indeed as you describe, then the fuel injection pump is likely the culprit. I know of an AFN engine where it started similarly: intermittent starting problems that progressively worsened. The cause was broken springs in the high-pressure part of the fuel injection pump.

Based on how you're describing it, I'd suspect the KW screw. Even though it's only 20,000 km old, there's no guarantee that the KW shaft hasn't worn out, and that the timing gear isn't 'slipping' on the shaft!

Even though it has nothing to do with starting the engine, I don't understand what you're saying about boost pressure.

"0.8 bar at standstill" - Is this overpressure? Where does it come from? That sounds like a lot.
"1.2 bar in the third gear at full load" - that's too much as well.

"Not enough boost pressure... so the wastegate is leaking?" Huh?? Why does it have to be the wastegate? It could also be a faulty turbo. Besides, you're not getting too little boost, but significantly too much.

Is the Trekker somehow modified or "chipped"?
How much of it actually happened?

m;

I found the whole thing about the turbo boost pressure a bit strange. Since my laptop isn't working at the moment, I told a friend from VAG, and he brought over the VAG tester (the new, large one with the TFT screen). He said it should be showing something like 2.2 to 2.3 bar of boost pressure.

'Does anyone know where that measurement was taken? It definitely wasn't read using an analog boost pressure gauge, but electronically.'

The LLK definitely has a hole in the plastic.

Laufleistung etwa 170tkm. No chapter!

The KW screw is as tight as it should be!!! I don't believe that the KW wheel would wobble on the shaft after 20000 km if the screw was properly tightened. If that were the case, the injection timing would also be affected. However, the injection timing is perfectly stable.

I've also been typing in the direction of 'pump,' but I hope not.

PS:
Question: Where does the VAG tester measure the boost pressure? Shouldn't it be around 0.8 bar under full load? Or is my friend, who works with TDI engines every day, mistaken?

Regarding boost pressure.

First, it's important to know what boost pressure we're talking about.

"Normally," the charging pressure is around 0.9 bar, with short overpressure peaks of up to 1.2 bar.

VAGCOM and all other electronic testers query the boost pressure from the engine control unit, which measures the pressure itself and has a hose connected to the intake manifold for this purpose.
That value represents the absolute pressure, which is the sum of the ambient pressure and the pressure increase due to the charging.
These are values that are approximately 1 bar higher than the charging overpressure.

If you knowingly have a leak in the coolant system, I wouldn't drive the car anymore, because you'll likely damage the turbocharger. This happens due to the feedback loop in the turbocharger's pressure regulation system:

The MSTG (Manifold Absolute Pressure sensor) is measuring too low of a boost pressure, so the boost control valve is reducing the pressure on the wastegate, causing it to close "more," which allows the turbo to spin faster and generate more boost.
If nothing works, the MSTG will go into emergency mode with a 00575 error.
If it's barely working, the turbo will be spinning at a very high RPM to generate the required pressure (it's like having 1.5 bar of boost, but only 0.9 bar actually reaches the intake manifold).


But, as I said, that won't have anything to do with starting problems.

Exactly what you described in the last few lines is true.
However, the boost pressure is still so high that no error code is being stored in the engine control unit (ECU).

The turbocharger takes far too long to reach maximum boost. It's probably spinning 'wildly.' I have no idea how long I've been driving like this. I've driven about 15,000 km, and I feel like the Passat has poor acceleration (over about three months).

'Because of the issue, I'm going to install a pipe instead of the LLK (likely referring to a specific component) for now to protect the turbo. I'll see if I can find a used one first. But even new ones aren't that expensive.'

Regarding the issue, I'm going to put a pipe in instead of the LLK for now to protect the turbo. I'll see if I can find a used one first. But even new ones don't cost that much.

And why the makeshift repair with a pipe? That's not exactly good for your tractor either.

Regarding the issue, I'm going to install a pipe instead of the LLK for now to protect the turbo. I'll see if I can find a used one first. But even new ones don't cost a fortune.

And why the trickery with a pipe?? That's also not necessarily good for your tractor.

Hello,
The missing coolant has a much smaller impact on the ATL (Automatic Transmission Liquid) than the leak in the coolant system!
Best regards,
Günther.

Hi,

Don't you think it would be much easier to repair the hole with a two-component adhesive and a suitable support material? If the hole isn't too large, this could even be a permanent solution and would definitely be less complicated than fitting a new pipe.

Try using the search function... there was a thread a while ago where people were discussing how to fix a LLK.

I read between the lines that you have a 1Z... is that correct? If so, then your friend was giving you incorrect information about the target pressure – Dieselmartin provided the correct values, and they are also listed in the target values section of the technical article.

The fact that he works on TDI engines at VW every day is irrelevant... In my Seat workshop, the master mechanic wasn't even familiar with the function of a VTG (Variable Turbine Geometry) and its associated control system.

Best regards,

Jan.

Now I'm a little further along, or perhaps even more confused.

Regarding boost pressure:

Today I removed the bumper and checked for the leak. In the end, the spot I had previously patched on the lower radiator hose was still sealed. So, it was a misjudgment on my part, as I thought the hole had reopened.

I couldn't find any leaks in the hydraulic lifting system (HLS) or the charging circuit, except for a slight oil leak at the bottom of the HLS unit (not from the hose itself). This indicates that the crimped connection is no longer 100% tight. However, I also couldn't detect any air leaks, even when running at full throttle.

Aufgefallen ist mir das bei eingeschalteter Zündung das LDR-Ventil ständig Takkert (ohne das der Motor an ist) !? IIs that normal?
Unterdruckleitungen zum Turbo hab ich geprüft. Are they all sealed?

Regarding difficulty starting:

Apparently, it only starts poorly after I've driven a short distance. This morning, it almost didn't start at all. After about 30 seconds of struggling, it eventually started.
He tried to start it occasionally, but it wouldn't turn over.
After it started running, I turned it off again after about 30 seconds and then restarted it. It started up immediately, but ran unevenly for about 4 seconds. After it warmed up, it started up perfectly again.

It apparently has nothing to do with how long the car has been parked. My wife took the car to work last night, and it started without any problems. She then drove about 3 kilometers home, and I tried to start it about 3 hours later. See above!

Before the incident, he had run for approximately 200 km on the Autobahn and then remained stationary for about 4 hours.
It definitely started for her, and the outside temperature was about the same.

The error codes aren't showing anything, and there are no air bubbles in the lines. The fuel tank vent is working correctly. The valve timings are also correct. The crankshaft pulley is perfectly secure (and it's also new).

Regarding the turbocharger issue, it seems we're left with either a faulty turbocharger or a problem with the boost pressure control system, possibly a malfunctioning vacuum actuator. I'm leaning towards the latter, as it sometimes seems to have its full power. I'll check that next week. The remaining question is: why does the solenoid valve for the boost pressure control make a ticking noise when the ignition is on?

Regarding the starting issue, I'm at a loss. Unfortunately, I'm currently unable to read any measurement data because my laptop isn't working.
Normally, in situations like this, wouldn't he store an error in the memory? But he's not doing that.

Hello,

Just a thought regarding the poor starting behavior:
It has been reported in this forum on several occasions that warm TDIs have difficulty starting. The cause is often a faulty coolant temperature sensor.
Now, the problem seems to occur mainly when the engine is cold, but it might still be related to that.

Perhaps it's the coolant temperature sensor in this case, as its values are used in the fuel injection calculation. I'm not sure, but I also believe that the coolant temperature affects the start of injection. Maybe that explains the initial white smoke.

Best regards, Georg.

P.S. There are many "maybe's" in this text, and these suggestions should only be understood as ideas for troubleshooting.

Okay... the matter has been resolved.

I sold the Passat to someone in Russia before I started replacing the pump and the turbo.

I now have a 1998 Golf III TDI Joker with 90 horsepower (same engine ). It has only 87,000 km on it. It's a complete AT (automatic transmission) unit from VW.

Hopefully, it will last longer this time!

Hello,

Making a diagnosis remotely is very difficult.

Sure, here is the translation of the text from German to English:

'Here are some questions:'

Have you already replaced or resoldered the power supply relay in slot 3?

2. Does your car have a small LED next to the button for locking the driver's door? If so, the vehicle has an anti-theft system with multiple relays soldered onto a circuit board, and these solder joints often break. This control unit is located on the driver's side, on the left, near the ventilation outlet - it's a bit hard to see (you need to remove the lower panel) and is fastened with a screw; as far as I remember, it has 'RWD' written on it. Remove it - open it - inspect the solder joints (for cracks) - resolder them. This control unit interrupts various power supplies.
Both of those things can cause problems with starting, and potentially lead to poor engine performance or intermittent stalling, but they are not the cause of your turbocharger issue!

Please double-check before you proceed!

I hope it's useful to you .

How is he supposed to continue searching, in Russia, using remote diagnosis?

Sorry .

My mistake; one should really read beforehand before writing.
Unfortunately, I didn't do that anymore and I completely put my foot in it .
Well, maybe the Russians who bought it are also in this forum .
Maybe it will help those .

If anyone comes across this thread again:

Relay 109 was not the issue, and the vehicle did not have an alarm system. The immobilizer was also functioning correctly.

If the immobilizer is defective, the vehicle would start but then turn off again after about 1 second, without any white smoke or other visible signs.

The spark plugs were also fine. Both filters were new, and he also had compression.


Final diagnosis:

Difficulty starting; pump failure.

Low boost pressure; the boost pressure control mechanism in the turbocharger is clogged or burnt. I couldn't get it working properly anymore. It was simply sticking and occasionally getting stuck.


The amount of work required and the cost of spare parts were not proportional to the age of the vehicle. Nevertheless, I still managed to sell it at a profit. I drove it for 1 year and about 75,000 km, and I made a good €500!
That's the way to live!