ALH: Delayed Acceleration - Explained

Hello,

"I recently acquired a 1.9 TDI ALH engine (66 kW, VP37 with VTG turbocharger) from a friend. The problem is that under full throttle, it sometimes struggles to rev up to around 2300-2400 RPM, and then suddenly pulls with full power starting at approximately 2400-2500 RPM."

The following has been checked:

- No error codes stored.
- VTG, easy to operate.
- Intercooler circuit sealed.
- Injector nozzles inspected, opening pressure and spray pattern excellent.
- Injection start verified.
- Exhaust system leak.
- no soot
- Full power, maximum speed is easily achieved.
- The LMM (mass airflow sensor) is an original VW part and has been used for 10,000 km.



Do you have any other ideas? I'm quite at a loss.

AGR heavily contaminated, may occasionally seize.

That would be a great tip...

The EGR valve was replaced in 2008, and I haven't looked at it since. Given that the car also has nearly 200,000 km on it, I was also considering removing the entire intake manifold behind the EGR valve and cleaning it with throttle body cleaner. It's probably quite dirty inside by now.

The question here is simply, how great is the risk that you might shear off the studs...?

Ibiza1986 wrote:

The question here is only how great is the risk that one will shear off the studs...

Normally, it's not a problem. They're not like the bolts on a turbocharger; they're just regular Allen screws. They also have this peculiar, typical VW green coating. They usually don't rust at all.

Okay.

Do you have any experience or insights on whether cleaning the channels would be beneficial for a stock engine?

Well, it definitely involves a certain amount of work.


Greetings.
Georg.

Ibiza1986 wrote:

okay, Do you have any experience or insights on whether cleaning the channels would be beneficial for a stock engine? Well, it definitely involves a certain amount of work. Greetings. Georg

In a series, it usually takes something really extreme to happen.

If the turbocharger takes a long time to build boost pressure, I would check to make sure everything is okay, including whether the vacuum sensor is able to activate properly.

Best regards, Rainer.

Ibiza1986 wrote:

Do you have any experience or insights on whether cleaning the channels would be beneficial for a production engine that hasn't been modified?

It won't hurt, but don't expect miracles. I cleaned my intake manifold last winter, during the complete removal of the EGR system. To be honest, I didn't notice any difference. However, it was only after 64,000 km, so there wasn't much buildup yet. As Rainer already mentioned, if there are very thick deposits, it will definitely make a difference.

Okay, I think I'll remove that thing and put a lens in there... If the channels are only slightly affected, I'll leave it as is... I'll definitely clean the EGR valve.

I completely replaced all the hydraulic hoses for him about a year ago, but I'm still going to double-check everything.

Could it be that the N75 valve is malfunctioning without any error codes being stored? Because a faulty N75 valve could also lead to problems with the VTG (Variable Turbine Geometry) system, which in turn could cause a lack of power at low RPM.

What comes to mind is this: I haven't replaced the vacuum line to the VTG sensor. It's located in a gray protective sleeve, and at the bottom, it's secured to the VTG sensor with a metal clamp. Until now, I wasn't clear on how to access it and cut through it .

That means this piece of hose is 200,000 kilometers old, but it still looked okay, so I left it. It's going to be fun to install another hose clamp down there; I'm looking forward to it.

Ibiza1986 wrote:

Could it be that the N75 valve is malfunctioning without any error codes being stored?

Because an N75 valve that isn't regulating correctly could also lead to VTG (Variable Turbine Geometry) errors, which in turn could cause a lack of power at low RPM.

Ibiza1986 wrote:

Rare, but possible. ...and is securely fastened to the bottom of the VTG container with a metal crimp clamp; until now, I wasn't clear on how to access it and cut through it

.
So, for me, it has always worked so far, with a strong pull. }

Despite the scolding?

I'm terribly afraid of accidentally damaging something Lader = expensive whenever I'm near a loading device. It's a basic level of caution that I've developed.

I'll take a look at it tomorrow, and of course, I'll make sure to get enough vacuum hose beforehand.

Ibiza1986 wrote:

despite the fine?

Yep. It's always worked so far. And don't worry, a turbo like that isn't made of sugar. I don't think you'll have biceps like Schwarzenegger. You definitely won't rip off the VTG canister.

I think that if I manage to do this, I'll also have to create a thread like the one about the cotton swabs .

Okay, I'll start with the vacuum lines. I think that's the quickest and cheapest solution. Then I'll put a hose clamp on the bottom and that's it.

Ibiza1986 wrote:

I think that if I manage to do this, I'll also have to create a thread like the one about the cotton swabs

.
If he reads this.

Ibiza1986 wrote:

..and then I put a hose clamp on the bottom and it's done.

You can leave it off. I think that clamp is pointless anyway. There aren't any on the solenoid valve or other components, and they still seal properly. I don't have any on mine either, and it works fine.

Yes, essentially, there's a vacuum applied, and the hose is being drawn onto it, so to speak.

Yes, if he reads this... *covers all the engine vents*.


I think the prices are outrageous... The dealership charges around €15 per meter for the hose, but I order it from a parts supplier for, I think, €1.15/meter, or maybe under €2/meter.

I struggled with that clamp for half an hour, it was such a pain.

The hoses looked good, but I replaced them all anyway, since I can't see underneath the fabric.


"But what I noticed is that the air intake pipe behind the mass airflow sensor, towards the turbo, is quite oily at the point where the cylinder head ventilation is also connected. Should I replace it? It seems to be leaking from a seam."

However, it's located before the turbo, meaning there's a vacuum there, so nothing can actually be "forced out," but only "sucked in."

Therefore, it's likely that air is escaping from the ventilation hose/pipe, as there's still pressure buildup there. I've cleaned it for now and will keep an eye on it.