Zu langsamer Ladedruckaufbau? | Posts 48+

DocSnydor wrote:

The performance is virtually identical with and without the catalytic converter.

Hi Doc.

That pretty much rules out the exhaust.
Now that you've cleaned the intake manifold, the airflow should be clear (unless the channels in the cylinder head are still significantly constricted by oil sludge).

Just to clarify: Are you also experiencing a drop in the mass airflow (MAF) value at higher engine speeds, even with full boost pressure?
If so, it could also be an electronic fault.

To completely rule out the LMM (Mass Air Flow sensor) as the cause, you can try connecting a diode (e.g., 1N4002) from pin 1 (5 volts) to pin 6 (the measurement pin) of the LMM connector.
The engine control unit should always recognize an excessively rich air-fuel mixture.
If the LMM value drops, it's likely due to the engine computer itself .

Hi Ulf,

There was probably a small misunderstanding.
The mass airflow sensor (MAF) value isn't dropping, and that's how the car is driving.
I've already driven several thousand kilometers without a mass airflow sensor (MAF), using a diode instead. That gave me a slight increase in power back then. My MAF sensor probably wasn't the best anymore, but it was still okay.
I suspect the problem is more likely located somewhere in the cylinder head. Perhaps the hydraulic lifters .
The engine sounds strange, almost metallic. Back then, when I took it to Bosch service, they told me that one of the cylinders was 'misfiring' or 'gurgling.'
I recently checked the values from the error database again at 3000 RPM, and everything was okay there.
Sometimes the car (subjectively) runs better intermittently, even though the turbo boost behavior doesn't change (I have a fixed LDA). But subjective observations don't always tell the whole story...


Best regards.
David.

DocSnydor wrote:

I suspect the problem is more likely located somewhere in the cylinder head. Perhaps the hydraulic lifters . The engine sounds weird, almost metallic. Back then, when I took it to Bosch service, they told me that one of the cylinders was somehow "gurgling."

Hi David,

If something were wrong with the hydraulics, one should be able to recognize it, in my opinion, by some kind of "irregular" valve noise.

Have you ever done the downhill compression test (-> used car tips)?

If that doesn't lead to anything conclusive, you could, for example, perform a "proper" compression test.
Connect the crankshaft position sensor to an oscilloscope, disconnect the wiring harness from the starter motor, and connect the starter motor terminal to the positive battery terminal.
At the crankshaft speed where compression begins to build, you can already see "significant" compression values, and cylinder differences can be identified on the oscilloscope by observing the time intervals between the sensor peaks.

The question is, which one is more readily available to you: an oscilloscope or a regular diesel compression tester... I just happen to have an oscilloscope from my electronics projects.

It still seems possible that a restriction in a cylinder head intake port or at a valve could be caused by oil sludge. This could potentially also change the intake noise of the affected cylinder, perhaps towards a gurgling sound...?
(Or have you checked and cleaned the ZK channels, including the valves?)

Such significant bottlenecks become increasingly apparent with increasing engine speed, leading to power loss due to poorer cylinder filling.
While it's true that the cylinder in question could eventually start to produce carbon deposits if less fresh air enters than is required for the combustion of the injected fuel.
But subsequently, the black smoke from this cylinder is diluted by the "clean" exhaust gases from the other cylinders, so that you may not see much soot coming out of the exhaust at all. . .

Hello DocSnydor,

While the topic here is quite well-worn, after reading everything, I think there might be something wrong with the wastegate on your car.
If a Passat with 90 horsepower can reach a speed of 210 km/h, then, in my opinion, the 90 horsepower figure is definitely accurate.
However, sludge in the intake manifold and a clogged catalytic converter would first manifest as a noticeable reduction in peak performance.
A wastegate that doesn't close properly can definitely cause symptoms like the ones you described.
If I were you, I would take a closer look at the turbocharger.
Or, if that's too complicated, you could check eBay.
With a little patience, you can find a turbocharger for testing at a reasonable price.

Best regards,
Albrecht.

@DocSnydor:

How about, instead of your "diode solution," you try connecting the good old mass airflow sensor again? Then you could verify my measurement.
If you're experiencing the same LMM (lambda measurement module) value drop as I am, then we can be sure that our engines are experiencing the same problem.

What do you think about it? It shouldn't be too much trouble.

Regards,
Alex.

Albrecht wrote:

If a Passat with 90 horsepower runs at 210 km/h, then, in my opinion, the 90 horsepower are definitely the reason.

Hi Albrecht,

"When driving at 210 km/h, it only seems to work when going downhill. On a flat surface, the speedometer shows around 180 km/h, which is probably lower than the expected 190 km/h. However, this brings us back to the uncertainties caused by headwinds and unnoticed inclines/declines..."

Quote:

Sludge in the intake manifold and a clogged catalytic converter would first manifest as a noticeable reduction in peak performance. A wastegate that doesn't close properly, on the other hand, clearly exhibits symptoms like the ones you described.

I agree that the slow build-up of boost at the bottom end is a problem. However, if the wastegate "closes enough" to ensure full boost in the mid-range, then it should definitely also allow for it in the upper range (in fact, it might even need to open a bit further to prevent excessive boost!).

That means the power loss at the top end cannot be explained here by a wastegate that is not closing properly.

Hello Ulf,

Quote:

"When driving at 210 km/h, it only seems to work when going downhill; on a flat surface, the speedometer shows around 180 km/h, which is probably lower than the usual 190 km/h. But then we get into the uncertainties related to headwinds and unnoticed inclines/declines..."

"It's too subjective to talk about the top speed. However, I don't think a speedometer reading of 180 km/h is too little for a Passat with 90 horsepower and over 200,000 kilometers on the clock. It's supposed to have a top speed of around 175 km/h, right?"

Quote:

But if the wastegate "closes enough" to ensure full boost pressure in the mid-RPM range, then it certainly does the same in the upper RPM range (in fact, it must open even further there to prevent excessive boost pressure!).

"You are absolutely correct, and I didn't dispute that. However, this is Donalexo's car, and I thought it also lacked power in the higher RPM range! There must be something else going on. If the full boost pressure is reached too late, but then regulated properly, in my opinion, this almost exclusively points to a wastegate that isn't closing correctly. The normal opening point should be around 2000 RPM. Below that, it should be completely closed. However, if some pressure is always leaking, this point shifts to a correspondingly higher RPM (e.g., 2500 RPM), and below that, the desired boost pressure logically cannot be reached."
I would definitely start by checking these things first, given the symptoms described.

Best regards,
Albrecht.

Hello Ulf,
'It's too subjective to talk about the top speed. However, I don't think a speedometer reading of 180 km/h is too little for a Passat with 90 horsepower and over 200,000 km on the clock. It's supposed to have a top speed of around 175 km/h, right?'


'You're right, the registration document states a top speed of 178 km/h...'
But the thing is, I don't just reach 180 easily. It takes a lot of patience.
I would describe it like this: The car feels like it has a large trailer attached to the back. Once it's rolling, it's okay. But accelerating is a real effort. It's especially noticeable when driving uphill.
Recently, I checked the idle speed control again. Now, my new highest value is 0.7 (previously it was 0.4).

@Ulf
Okay, I think I'll be able to get a compression tester more easily than an oscilloscope .
I'll probably tackle that soon. Will it also give me information about the condition of the valves and lifters?
I didn't modify the cylinder head itself because I clearly lack the knowledge and the tools for that. So, it's quite possible that the intake channels are still partially blocked further inside...

@Alex
Okay. I'll check that out next week with the LMM. It's still installed, but not connected . It would be best to log the LMM values, right?

@Albrecht
'Since I have a fixed LDA (Lambda-regulated direct injection) system installed, I can always monitor the turbocharger boost pressure. Above 2500 RPM, I have full boost pressure, but still lack power. So, I'm going to disable the turbocharger for now...'

DocSnydor wrote:

Okay, I think I'll be able to get a compression tester more easily than an oscilloscope. I will probably tackle that soon. Does that also give me information about the condition of the valves, Hydros?

Hi.

As far as the result "compression" is concerned, of course yes .
Worn valve guides and/or excessive clearance due to valve lifter issues do not necessarily have to manifest significantly in the compression values; however, the engine may exhibit increased oil consumption or louder valve clatter.

I didn't modify the cylinder head myself because I clearly lack the knowledge and the tools for it. Therefore, it's quite possible that the intake channels are still partially blocked further inside...

Quote:

That would (unfortunately) be my initial assumption. Why would the sludge specifically

not accumulate in the cylinder head, which is essentially just a logical extension of the intake manifold up to the valve... and there's hardly anything to suggest that Alex's engine doesn't have the same problem, because I don't find that possibility particularly unlikely.
It was essentially confirmed in advance that removing the catalytic converter wouldn't make much difference, because a short restriction (only in the Z-pipe) ultimately works almost as well as a longer one (in the catalytic converter and Z-pipe).

Particularly insidious: if the engine is mechanically okay, sludge in the cylinder head is unlikely to noticeably affect the compression values at the low cranking speed.

@DocSnydor:

Quote:

@Alex Okay. I'll check that out next week with the LMM. It's still installed, but not connected. It would be best to log the LMM values, right?

Yes, exactly, that would be really great. Ideally, you could also implement similar boundary conditions as I have. I have a suitable "test hill," a remote stretch of road. The road also has a significant incline (about 8%), so the acceleration in 3rd gear will only be moderate. I think this is important because on flat ground, the boost pressure may not be able to keep up with the engine speed. And in 4th or even 5th gear, it's difficult to maintain an engine speed range of 1100-4500 RPM on a country road (top speed over 200 km/h!!!). I also logged data groups 3 and 11 in parallel.
With your help, I could finally get some comparative data for a wastegate turbocharger engine. It would be interesting to now have reference measurements from an engine that is "problem-free"! Can anyone help with that?

@ulf:
Well, maybe two effects are working against me: The added intake channels, including the intake manifold, primarily restrict airflow at engine speeds above 3000 RPM, while a slightly leaky wastegate prevents the turbocharger from spooling up properly at low RPMs.

Here's another short anecdote about the friendly person:
I went there today to get a "professional" opinion on the problem. The master technician was convinced that it was the mass airflow sensor (MAF). He was quite disappointed when I told him that a new MAF sensor had already been installed.
Actually, I wanted to persuade him to let me borrow his timing tool so I could quickly check the valve timing. However, he just responded with a slight smile and the comment: "Come by next week, and I'll take a look at it." He also pointed out that a misaligned timing is practically impossible in a TDI engine because even a single tooth misalignment would cause the valves to collide with the pistons. He seemed unaware that the camshaft wheel in a TDI is only attached with a friction-fit conical connection, which means "stepless" misalignments are possible.
The next expert tip from the master was aimed at the turbocharger. He probably wants to sell me a new one. You can certainly make a good amount of money with that!!

I might try again with another dealer to see if I can borrow their alignment tool.

So far, so good (or rather, not so good).

I will keep you updated.

Regards,
Alex.

Hello Alex,

Quote:

He also pointed out that with a TDI engine, practically no misalignments can occur, because even a misalignment of one tooth would cause the valves to collide with the pistons.

He's right! With a TDI engine, you don't have much clearance between the pistons and valves. In my opinion, it can't be adjusted that much (without causing damage) that the performance suffers so drastically...
He's also right about the loader.
The master wasn't that foolish.

Albrecht wrote:

The master wasn't that stupid.

Hi.

First, they want to sell you the usual new LMM (too bad, it's already been replaced ), then a new loader , and if the problem still persists after that...
then, suddenly , the clogged intake path is discovered, and its cleaning is, of course, very time-consuming and therefore expensive again, after 2 (presumably unnecessary) equally expensive parts have already been replaced - if it had gone according to the master's plan .

And such residue from the EGR valve, the mechanics had never seen before . . .

No, the master isn't really stupid, but it's still somehow typical .

I still believe that all these problems could only be caused by the suspected residual sludge in the ZK (zinc collar), so the charger could very well be okay. See above (self-quote):

Quote:

In my opinion, your problem can be explained by a bottleneck in the gas passages, which restricts the gas flow despite full boost pressure, especially at higher engine speeds -> the mass airflow sensor (MAF) value (as cylinder filling per stroke!) drops significantly. In the lower RPM range, the throttle restricts the boost pressure that is just beginning to build, making it more difficult and thus shifting the engine's operating range towards higher RPMs.

Hi Ulf,

Quote:

I still believe that all these problems could be caused by the remaining residue in the ZK (charging unit), so the charger itself might be perfectly fine

.

It would actually be quite good if you turn out to be right.
The question that then arises is how to remove all that gunk from the intake channels without having to remove the cylinder head for cleaning.
Is there a reasonable method for removing deposits from the intake manifold when the intake manifold is removed and the engine is otherwise disassembled?

The risk of damaging the engine during cleaning is quite significant. No abrasive products or (parts of) cleaning tools should fall into the engine. Furthermore, I can't imagine using harsh chemicals (e.g., brake cleaner, Loctite cleaner, gasoline, etc.) in this area, as there's always a risk of flooding the cylinder. What do you think?

Regards,
Alex.

donalexo wrote:

Is there a reasonable method to remove deposits from the intake manifold when the intake manifold has been removed, and the engine is otherwise disassembled?

Hi Alex,

Good question, next question... I haven't done anything like that before.

In any case, I would make sure that the intake valve of the cylinder being worked on is closed, because then something can slide down without directly ending up in the cylinder.
And you have the opportunity to carefully remove the material, for example, using cloths soaked in a sticky substance attached to a suitably curved wire or similar.

A mirror and lighting to "look around the corner into the canals" would definitely be included for my transversely mounted engine.

Quote:

Furthermore, I can hardly imagine that one can use harsher chemical agents (e.g., brake cleaner, Loctite Cleaner, gasoline, etc.) in this area, as there is always a risk of flooding the cylinder with them.

"You're right. If something like that were to happen, I would slowly rotate the engine in reverse to push the debris back towards the intake, and then use rags to soak it up there."

@ Alex and everyone else,

Sorry for the delay, but attached (hopefully I've done this right) is the log file from my car with the MAF sensor plugged in, as promised.
Okay, so I logged groups 3 and 11. I drove up a steep hill on the 3rd floor, just like you did...
I'm curious to hear your thoughts on the data and whether you're seeing similar results. One thing that's definitely noticeable is the air value, which decreases at higher RPMs.
Well, take a look at it...

Best regards.
David.

P.S.: Don't left-click on 'Download,' but instead choose 'Save target as' and then open it with Excel. Otherwise, the file might seem a bit confusing *lol*.

Hi Ulf,

I still believe that all these problems could be caused by the remaining residue in the ZK (charging unit), so the charger itself might be perfectly fine.

It would actually be quite good if you turn out to be right.
The question that then arises is how to remove all that gunk from the intake channels without having to disassemble the cylinder head for cleaning.
Is there a reasonable method for removing deposits from the intake manifold when the intake manifold is removed and the engine is otherwise disassembled?

The risk of damaging the engine during cleaning is quite significant. No abrasive products or (parts of) cleaning tools should fall into the engine. Furthermore, I can't imagine using harsh chemicals (e.g., brake cleaner, Loctite cleaner, gasoline, etc.) in this area, as there's always a risk of flooding the cylinder. What do you think?

Regards,
Alex

Hi Axel,

I have the following idea for cleaning the intake shaft:
Bring the motor to the position where the relevant valve is closed. Then, scrape out any accessible dirt. Any debris that has fallen inside can be vacuumed out using a vacuum cleaner with a suitable hose attachment.
To further verschandeln around the corner, a metal bottle brush might be useful. If it's flexible enough, you might even be able to attach it to a cordless screwdriver, turning it into a kind of dirt-removing tool.
Oil-stained dirt can perhaps be best removed with gasoline or a similar solvent. However, when using a vacuum cleaner to suck it up, one must be careful that the fumes do not ignite near the collector sparks inside the vacuum, which could then cause the vacuum cleaner to spread the dirt throughout the entire workshop .
Perhaps it would also be a good idea to blow compressed air into the cylinder through the spark plug opening (with the intake valve open) and then dislodge the dirt (using a dust mask and safety glasses ).
'How tight is a valve actually? Would gasoline stay in it overnight, or would it leak through? Maybe it would be a good idea to do some engine cycles without the spark plugs first, and then change the oil.'

Regards,
Eike.