Passat AJM: Troubleshooting Acceleration Issues

Hello,

Help for a Passat driver. Please read the following text and help me understand what it could be.

It's a Passat Variant TDI PD (with 115 hp, engine code AJM), manufactured in May 1999, with 53,000 km on the odometer.


In September of last year, a chip was installed by ******** Tuning from Austria (W. G.).

The increase in performance in the lower RPM range was quite impressive. At higher RPMs, there seemed to be almost no change (not even in top speed - possibly 3-4 km/h, but no more!). The car has never been on a dynamometer.


The consumption seems to have increased slightly. The maximum average is 0.5 liters (less with economical driving, and correspondingly more with full load).


If anything, it seemed that the car produced slightly more soot than it did before the tuning. It was hardly ever visible in the rearview mirror.

BUT things have been different for a few weeks now.


The acceleration (from low speeds) has become less impressive. When compared to other Passats with 110 horsepower, you can barely keep up (despite having a 115 horsepower engine and a chip).

The maximum speed is still just under 200 (and only achievable after a long run). Reaching speeds of 180 to 190 km/h is relatively quick.


"Furthermore, the car now emits excessive black smoke when you accelerate hard from low RPMs (1400 to 1900 RPM). It leaves a thick cloud behind, making it difficult to see the cars following. Above 1900 RPM, the cloud dissipates (or at least spreads out more)."

The AGR (Abgasrückführung system) was disabled, but a few weeks ago it was reconnected to see if any difference in fuel consumption could be detected.

"As a Passat driver, I..."
I have removed the LMM (Bosch 028 906 461) – it's right here in front of me. The metal rods on the sensor appear to be clean (shiny) on the right side. I'm not sure if I should use brake cleaner on them? Could I damage anything with it? The LMM hasn't been checked by the workshop yet.

After reading so much in the forum, I'm starting to doubt that the problem is related to the mass airflow sensor. I'm not experiencing any jerking, and the maximum speed seems relatively consistent (although I haven't been able to go faster than 190 km/h recently, probably because the road was too crowded). The idle is smooth.

About 8 weeks ago, I experienced a mysterious malfunction. Shortly after starting the car, it would jerk strangely, and it would stall at traffic lights. It felt like it was only running on 2 or 3 cylinders. The power was completely lacking. However, it seemed to improve somewhat at higher RPMs. When I turned it off for 10 minutes and then tried to start it again, everything seemed to be fine...!?

The workshop immediately read the error codes, but couldn't find any errors. Afterwards, it sounded like it might have been the mass airflow sensor (MAF), right? It's strange that it started working again afterwards. I can't say for sure whether I've experienced increased soot in the lower area and slightly reduced acceleration since then.

Someone online wrote to me suggesting that the turbocharger boost hose might be faulty. Do you think that's possible, or do you have any other ideas?


How can we help him?

Greetings to you, Peter.

hi peter,

'To me, it sounds like there's not enough boost pressure! I had something similar with my 1Z engine before. There were leaks in the charge air system. Check that!'

'Could you please log the data for the air pressure and airflow? You should be able to quickly determine what the patient is suffering from!'

Hi!

If the engine is producing black smoke (soot), the mass airflow sensor (MAF) can almost be ruled out. If it's defective, it reduces the fuel injection amount, which doesn't necessarily increase fuel consumption, unless you try to compensate for the reduced power with aggressive driving. Since you can't give it full throttle, and the efficiency isn't affected.
Excessive black smoke suggests a leak in the intake system that is not being detected by the engine control unit. However, this single occurrence cannot be explained in this way.
The chip increases the boost pressure, which can quickly lead to a failure in a weak point. Your friend should check the intake system for oil leaks, especially the intercooler. He should do this soon, as the turbocharger could overspin.

Best regards,
Uwe

Hello everyone!

Thank you, the search continues. I will report back.

Greetings, Peter.

Hello Mc_Givertechnik.

I've already had the problem where one of the fuel injectors stopped working.
worked correctly.

The injector nozzle was clogged with a piece of debris.
However, under normal operating conditions, this noise was not audible.

The problem was first identified during testing on an injector test bench.

My tip:

Find a good diesel repair shop near you that also has the necessary equipment.
It has testing equipment.
For example, a dynamometer including a data logger, as well as test benches for...
Fuel injection pump or the fuel injectors.

I'm not referring to a dealership or any other type of official repair shop.
Based on my experience, they will definitely go to the diesel specialists.

If you want an address, I might be able to provide you with a good one.
Workshop recommendation.

Regards,
Hturbo01