ARL: No Power at Low RPM

Hi there.

As the title suggests, my car has no power in the lower RPM range. It doesn't really start to pull until 2800 RPM, whereas before it used to have power as low as 1500-1800 RPM.

I replaced the turbocharger, and on the first drive, after about 200 kilometers on the highway, this phenomenon occurred.

Following several discussions, another new turbocharger was installed, this time by a specialized workshop, as I suspected I had made an installation error myself.

The error remains.

Switched:
Mass airflow sensor.
AGR valve.
Boost pressure sensor.
all three control valves.
Vacuum lines were inspected and partially replaced, and two turbo hoses were renewed.

I even jokingly used the vacuum pump to apply half a bar of vacuum to the turbocharger's control valve - still no power at low RPM. Then I connected the pump between the valve and the control valve - it turns out that up to about 3000 RPM, half a bar of vacuum pressure reaches the control valve.


The error is still present - the turbo boost comes too late. Initially, it would also trigger the limp-home mode, but the workshop did something, and now it doesn't go into limp-home mode anymore, but the power only kicks in from 2800 rpm.

The car sat for about half a year because I was fed up with it. Now I've purchased a VCDS system through Mr. Kaufmann, and I finally want to get to the bottom of the problem.

"Our workshop declines the vehicle, stating, 'You need to tell us what's broken. We don't do troubleshooting. How can we bill you if we don't find a fault?'"

Well, tomorrow evening I'm going to do a log trip. I've found instructions on how to do it, and I still need to find a straight stretch of highway.

Achso, wenn man bei über 3000 u/min, wo er jetzt ja normalerweise Leistung hat, vom Gas geht und wieder drauf geht, braucht er lange bis er wieder Leistung hat. Das fühlt sich alles nach einem Ladedruckleck an, die Schläuche habe ich aber ab Turbo bis Anfang AGR Ventil mit 2 Bar abgedrückt. Die stay close.

VCDS indicates a difference of almost half a bar to three-quarters of a bar between the target and actual boost pressure below 3000 RPM. Above 3000 RPM, the values are almost the same.

Sure, here's the translation:

"Something else:"

The article "Common Mistakes of TDI Divers" states the following:

"Please provide the text you would like me to translate from German to English."
Symptoms: Intermittent or constant lack of power in certain or all engine speed ranges, occasionally "acceleration dips" in specific engine speed ranges.
Full power is sometimes only available for a short time after the engine is started or when the accelerator is released.
Occasionally, error messages such as "Intake manifold pressure control differential" or "Forced induction pressure control exceeded limit" may appear.
Boost pressure indicator (if available) shows unusual/incorrect values.
Common causes: Faulty boost pressure control or turbocharger.
If the boost pressure is too low, also consider the possibility of leaks in the intake manifold (-> boost pressure too low in the lower RPM range)!
"Please provide the text you would like me to translate from German to English."

Quote:

Also, if the boost pressure is too low, also consider leaks in the intake manifold (-> boost pressure too low in the lower RPM range)!

Intake manifold? What does that mean?

Best regards.

Andreas.

Hello Andreas,

It probably should have been labeled "leak in the pressure pipe" or "blockage in the suction pipe (e.g., clogged filter)."

You can clearly see it in the 3.8 and 11 logs. Please do that, and then we can see if the air mass corresponds to the boost pressure.

Regards,
Guste.

I'm experiencing the same problem with two BKC engines. The turbos have been replaced in both (not by me). In one engine, the target/actual boost pressure is the same from 2150 RPM onwards, but at all lower RPMs, I have 0.3-0.4 bar less boost. I've already tried everything, and I've even driven without the exhaust, so directly after the turbo.

Origin of the loaders is unknown for both.

I just finished a log ride, with scores of 1/8/11.
The smoke limit is slightly below the torque limit up to 1800 UMD, and should still be controlled by the mass airflow sensor (MAF) in the BKC system.
I've also already adjusted the pre-tax rate curve, meaning the VTG (variable tax rate) is applied for a longer period, but that doesn't seem to make a difference either.

Do 3/8/11 again tomorrow.

Is there anywhere where vacuum pressure is lost?

Best regards, Rainer.

I still have a butcher here, and I've temporarily replaced the valve unit with the three valves. I've also replaced and checked several vacuum hoses.
Everything seems to be going well so far.

If I manually apply a vacuum of half a bar to the turbocharger, I should theoretically have power in the lower RPM range.

The VTG (Variable Turbine Geometry) is moving, but I'm not getting any power in the lower RPM range.

I just did some log runs in third gear. I kept the RPMs between 1500 and 4500 and then let the engine coast down.

3/8/11

You're stepping on the accelerator around 2 seconds in. However, the load detection (LD) doesn't activate until 11 seconds. From that point on, the torque limitation kicks in (before that, it's running in a "smoke-limited" mode due to the lack of LD). This makes sense, but it's clearly taking too long.

The VTG control system appears normal to me.

If it's not the exhaust being blocked, then in my opinion, the only other possibilities are the turbocharger itself or its direct control system.
So: Is the VTG moving smoothly and maintaining its position (injection test)? Is there sufficient vacuum pressure?

Possibly remove the exhaust and mechanically fix the turbocharger at its maximum boost level, and then CAREFULLY (!!!) take a test drive while monitoring the boost pressure. If it still doesn't increase, then the problem is the turbocharger. However, if the turbocharger was working correctly and you accelerate too quickly, you will definitely need a new one afterwards. So please be careful.

Regards,
Guste.

Thank you for the response.

I replaced the battery myself, and on a subsequent test drive, the error occurred after approximately 200 kilometers.

Since I suspected either an installation error on my part or a faulty charger, I had a new charger installed by a workshop. The problem persists.

Furthermore, as mentioned above, exactly half a bar of vacuum pressure is applied to the charging container.
If I manually apply a vacuum of half a bar to the container, I can see the rod moving.
When I start the car with the manually controlled turbo, I still don't have any power.

When I start the vehicle and observe the rod, I see that it is moving.

And what about the freedom of movement of the exhaust system?

I once spent a lot of time troubleshooting my air-to-water heat exchanger because of something similar. Definitely, 0.5 bar of vacuum pressure is not enough for this type of compressor.

I'd like to measure the vacuum pressure generated by the tandem pump. It should be between -0.8 and -0.9 bar at idle.
In idle, the VTG control valve should adjust to -0.7 bar. Otherwise, the turbocharger will not function as it should.

In my case, it was the vacuum pump. Before, it was producing a vacuum of -0.6 to -0.7 bar at idle. I installed a new gasket set, and now everything is perfect.

At the time, my car exhibited similar behavior, although not up to almost 3000 RPM. In my case, it only went up to around 2300 RPM.
I had tried and swapped out all sorts of things, but in the end, it turned out to be the pump-nozzle elements. Apparently, the amount of diesel being injected wasn't producing enough exhaust gases to drive the turbocharger, or simply not enough fuel was being injected.

Greetings.

Hannes.