ACV: Insufficient Power Output

Hello,
I'm having another problem with a T4 again.

Let's get to the key details:
Year of manufacture: 2002.
ACV
140,000 km
Gearbox.

Problem: Lack of power starting at approximately 2600 RPM.

While driving, a significant loss of power occurs starting at approximately 2600 RPM, and this is dependent on the gear.
"Further acceleration is very slow, and it takes about 500 meters to reach 3000 RPM."

While reading the measurements, I noticed the following:

(read: full load at 1500 RPM, printed at 3000 RPM)

Air mass: 220 mg.
Boost pressure: 1336 mbar.

The boost pressure and air mass are at their maximum until the engine reaches that magical RPM.

When the error occurs, the motor noise becomes "rougher" or "more pronounced."

During my troubleshooting, I have checked or replaced the following components so far.

LMM ern.
Boost pressure control solenoid valve.
Diesel filters.
AGR shut down.
Cat expanded by replacing it with an empty space.
Air intake duct from the air filter to the turbo (had a lot of play on the turbocharger).
Oil pressure checked.


All of this brought no improvement.

When comparing the fuel injection amount based on driver preference versus the default setting, I noticed that it drops dramatically.

"Driver request: approximately 46 mg, to be administered before 2600 RPM, then approximately 35 mg, followed by an additional 15 mg."

What's also noticeable is that when I give it gas while the car is stationary, the engine speed decreases on its own.
"So, with the pedal position remaining the same!"

Now, the question is:

Quantity-based signaling or not?!

Does anyone have any other thoughts on this?

I would really appreciate any feedback or suggestions. Thank you!

Basti.

Oh yes, I forgot, there are no error codes stored in the system's memory.

Basti.

brg wrote:

(read 3rd gear, full load from 1500 RPM, printed at 3000 RPM) Air mass: 220 mg Boost pressure: 1336 mbar. The boost pressure and air mass are at their maximum until reaching this magical RPM.

Is "air mass" a typo? If not: for example, does the bypass valve get sucked open, or does a too-soft intake hose collapse?

Quote:

When comparing the fuel injection amount based on driver preference versus the default setting, I noticed that it drops dramatically. The desired driver dosage is approximately 46 mg, to be taken before 2600 RPM, then about 35 mg, and then another 15 mg

Until then, I found it somewhat interesting, but after this sentence-less jumble of words, I'm simply giving up!

Hello,

No, the "air mass" part is not a typo!


@Ulf: Sorry for this "punctuation-less word salad"!

(Desired driver dosage is approximately 46 mg, to be administered before 2600 RPM, then approximately 35 mg, followed by an additional 15 mg.)

I meant that the intended injection amount should be 46 mg/h; however, the actual value is 15 mg/h.

I have already replaced the intake manifold boot.

Best regards, Basti.

Hi,

Your air mass values are far too low, so there are only two possibilities:
- Measurement errors, for whatever reason (incorrect mass airflow sensor installed, faulty engine control unit, faulty wiring, etc.),
- Clogging (exhaust system, EGR valve stuck).

Best regards, Rainer.

Basti, how did you deactivate the AGR?
a) Plugging the control hose or b) Installing a sealing plate between the EGR valve and the intake manifold?
If a), then please install a sealing plate. I've already had EGR valves that were mechanically...
couldn't hold it anymore.

Best regards,
Rudi

Good evening!

@ Rudi: I chose option b. Unfortunately, I sometimes forget to remove the plate again. So, exhaust fumes are out of the question.

@ Rainer: I have already replaced the mass airflow sensor (MAF). At idle, the air mass is in the 400mg range. It then continues to increase until this engine speed. I temporarily covered the MAF sensor with tape for about 2/3. The result was an air mass of about 800mg at idle and about 1200mg under load. It then ran for a kilometer as if "stuck," of course, with the corresponding fine particle emission across the entire speed range. However, in the second test run, the old problem reappeared. Unfortunately, I don't have any data about the fuel flow rate.

Before I remove the pump and take it to the Bosch service center, I'm going to drive it one more time without the exhaust system.
"Make sure that none of the pots are leaking."

Oh yeah, I just remembered, right before the error occurred, there was an entry in the error log.
Something about the accelerator pedal and exceeding [a limit]...

Thank you for your help!

I am always grateful for any suggestions.


Basti.

You can definitely leave the pump in; just make sure you're providing proper ventilation for your engine.

Best regards, Rainer.

Trying it without the exhaust is a good idea.

A friend recently had a problem with a small articulated loader: a rusted part in the exhaust system collapsed when the accelerator was pressed, causing a blockage.
He immediately buckled under the pressure.
He only discovered the problem by chance, and according to the manufacturer, the device was already considered to have a motor failure. He took everything apart and then put it back together again, all because of such a trivial piece of debris in the exhaust.

brg wrote:

I temporarily covered the LLM (Lambda Sensor) with tape to about 2/3. The result was an air mass of approximately 800mg in the LLM and up to 1200mg under load. It then ran for a kilometer as if "stuck," of course, with corresponding fine particle emissions Strangely, this occurred across the entire RPM range. In the second test run, however, the original problem reappeared. Unfortunately, I don't have any data on the flow rate

. The low injection volume is, in my opinion, only a symptom, but not the cause.

Allmählich wird für mich der Gedanke eines kollabierenden (Saug)Schlauches immer wahrscheinlicher. Taste mal alle Luftschläuche bis zum Ansaugkrümmer ab, ob sich irgendeiner irgendwo auffällig leicht zusammendrücken läßt. Wenn ja: exchange.
Similar effects could also be caused by foreign objects in the suction lines, which, above a certain gas flow rate, could be drawn in and lodge themselves in front of the next constriction – or a shut-off valve that closes due to a defect.

During the next test drive, we need full-throttle data logs.
a) MWB 8 and 10.
b) MWB 11 only.
It's interesting until the performance drops, as that's when you can better identify a hose collapse.

"In one ACV I worked on, the air intake to the turbo was leaking, causing similar symptoms. The plastic pipe connecting the air filter to the turbo was simply resting there without a clamp, and it could be moved about 1 cm in any direction by hand. After installing a clamp, it was much better. A new mass airflow sensor (MAF) then restored the original performance, as the readings from the old one were also insufficient."

I don't know if you've already checked, but I just remembered.

hello basti,
I also have the ACV block!
Your description sounds like a failsafe mode.
For me, the accelerator pedal was the cause!
Here are two possible solutions:
Increase the size of the buffer.
This can cause intermittent false signals that prevent the accelerator pedal from working.
The conductors will still be acceptable within the full load range.
2. Clean the accelerator pedal.
I removed and cleaned the electronic accelerator pedal.
Caution, but proceed with care and use a good quality electronic contact cleaner or similar product.

No problems since then!

The symptom was that the vehicle's engine control unit (ECU) would switch to a limp-home mode when there were sudden movements of the accelerator pedal.
Error description: Implausible signal!
sometimes, or only sporadically.

It was almost life-threatening when I was overtaking on the country road!
"If the car has no power for 2 seconds!"

best regards, leo

Hello,

Thank you for all the advice!


I'll start working on the conversion next week, assuming our 96 ACV is home.
It should be identical in everything except the engine control unit and the transmission.

I'll keep you updated!


Thank you!

Basti.

Hello, I found the error!
He is running!

Before I continued troubleshooting this morning, I drove around the block one more time. Strangely enough, I had power. Shocked, I drove around a second time, and sure enough, the problem reappeared. At first, I thought it might be temperature-dependent. It started when the temperature was -6 degrees Celsius, and then the problem occurred when the water temperature reached 60 degrees. However, after I couldn't find any connection, I started replacing the turbocharger hoses. When I noticed a soft spot and a strange deformation on one of them, I was almost certain I had found the problem. But as it turned out during the test drive, it was a mistake.
After having a cup of coffee, I simply detached the vacuum hose from the bypass valve.
And then, behold, it worked! I put the hose back on, and the error reappeared!

Tomorrow I'm getting a new valve. Then it should start running more smoothly again .

Thank you to everyone who contributed to finding the bug! And a special thank you to Ulf, who pointed me towards the bypass valve. Thank you!

Greetings from the remote region of Hohenlohe.

Basti.

brg wrote:

So, I simply detached the vacuum hose from the bypass valve. And then, behold, it worked! I put the hose back on, and the error reappeared! Tomorrow I'm getting a new valve. Then it should start running more smoothly again .

Um... which valve are you replacing? The EPW for the shut-off valve? I can hardly imagine that this thing senses certain engine operating conditions and then automatically switches the vacuum to the valve .
Then it should also happen even when the cable connector is disconnected.
If the error disappears without the cable, then the EPW is apparently receiving an incorrect control voltage and is itself innocent -> either a copper wire issue or a problem with the MSG module .

Hello,

Yes, that valve, Ulf.

Part number is 1J0906823A. I installed it today. I plugged it in, connected the hoses, and it started working. It has been running smoothly ever since. If I apply a vacuum of 600 mbar to the old valve using a vacuum pump and then gently tap or shake the valve, the applied vacuum drops. Normally, it should be closed when it's not powered. I suspect something is stuck inside the valve. I've experienced something similar with a boost pressure valve from a 1Z engine before.


Okay, you're welcome!


Basti.