ARL TDI: Power Loss & Limp Mode Troubleshooting

Hello to all you DIY experts,


First of all, please don't judge me if I describe my engine problem in a clumsy way, but I'm not very knowledgeable about engines. I hope you can at least help me a little bit.

Just to give you the basic details: I'm driving a Skoda Fabia (originally with engine code KBST: ATD), which has been modified with an ARL engine, a 6-speed gearbox, and all the necessary components.
'However, I still have the engine control unit from my ATD engine installed. The software was completely taken over from the ARL. Additionally, an OBD tuning was performed, resulting in 180 horsepower and 400 Nm of torque.'

Since the renovation, I've driven approximately 5000 kilometers, and everything has been running smoothly without any problems.

One day, while I was pushing my engine to its limits for a longer period, I noticed a strange hissing sound coming from the engine compartment. At first, I thought it might be related to the turbocharger, intercooler, EGR valve, but everything seems to be tight! I also couldn't find any oil leaks.
The problem was getting worse and worse (the hissing sound was becoming louder, there was a loss of power, and it was producing excessive smoke).
Under partial load, the motor operates normally; however, when running at full throttle, the control unit switches to emergency mode after approximately 4 seconds. After briefly turning off and restarting the engine, everything works again for a short time.
So, I went to the workshop and had them read out the error codes.


This resulted in the following: +Accelerator pedal position (possibly due to tuning???).
+Intake air temperature
+ Engine temperature (possibly due to tuning??)
+ System startup lock.
+Intake manifold vacuum (AGR deactivated?)

Furthermore, a deviation in the mass airflow sensor reading (0.5-0.6V, which is too high) was already detected when the engine was stationary.
'Tests of the turbocharger (control of the vacuum system, variable geometry turbine, pressure sensor) revealed no errors. What many workshops noticed was the excessively loud noise from the pressure sensor when it's vented. However, this phenomenon has been present since the beginning. (I suspect it might be due to an overly high boost pressure?) '

Unfortunately, I do not have VAG-Com.



Does anyone happen to have the actual vs. target data for a 180 hp version of the 150 hp TDI engine?

Our theories point towards either faulty software in the control unit OR a sensor malfunction.

I hope you can make sense of my description and perhaps give me some diagnostic tips. This troubleshooting process has been going on for almost 2 months now, and I'm starting to get really frustrated .



Thank you in advance for your efforts...



Best regards.
Martin.

Hi.

Quote:

There is no blow-off valve

for that engine; the boost pressure is simply reduced in a normal way.
The issues sound more like electrical problems to me, such as water in the wiring harness or the control unit.

Without wanting to promote anything: you won't get very far here without a diagnostic system. Target and actual values can be read directly from the engine control unit, provided the tuner hasn't tampered with it.
By the way, temperature sensors tend to fail frequently, so it's a good idea to check the values in the engine control unit for plausibility.

Is the catalytic converter/exhaust okay? If it's blocked, it can sometimes cause a whistling sound and make the engine run hot.

Best regards, Rainer.

Is he being scaled back?

So, the sound is like the air brake on a truck (when the compressor reservoir is full). It makes a really loud bang. You can also compare it to the sound of a pop-off valve (from gasoline engines)...


Hmm, if the tuner didn't mess anything up... I think he did. That's probably what it boils down to. I have an appointment with him on Thursday. Let's see what comes out of that.





Best regards,
Martin.

Quote:

So, the sound is similar to the air brake on a truck. (When the compressor reservoir is full.) It makes a really loud bang. icon_question.gif You can also compare it to the sound of a pop-off valve (from gasoline engines)...

Either a pointless showy pop-off valve was installed (-> get rid of that junk), or there's something fundamentally wrong (a leak caused by the intake air duct, or a blockage in the exhaust system).

Best regards, Rainer.

Okay, I definitely don't have a 'show pop off.' Is the original pressure sensor that is installed? (I didn't even know such a pointless thing existed ).

Exhaust blockage... The system was only manufactured a month ago. It's a complete stainless steel exhaust system. It could be my catalytic converter that's blocked. I need to have that checked out; thanks for the tip.




Best regards,
Martin.

Hello,
Finally, someone who understands and also drives around the area with an ARL conversion.
I also occasionally have some similar problems; yours sounds familiar to me.
First of all, I agree with Rainer that you need VAG Com or a comparable diagnostic software. Alternatively, you can visit a VW dealership and ask them to print out the error codes. The sudden, strong hissing sound you described, in my opinion, is likely caused by a leak in the pressurized side of the turbocharger system. It could be a small crack that only opens under high pressure, causing a sudden pressure release through the leak. This would also explain your sudden black smoke and power loss/limp mode. Carefully inspect the hoses on the intercooler; I had a small crack on the top side, directly below the metal connection point, which caused exactly the problem you're experiencing.

A more involved method is to use a compressor, but it provides very informative results. Close off the hose in front of the turbo (with a rubber plug) and attach a rubber hose (like a bicycle inner tube with a valve) over the top of the intake manifold, securing it with a hose clamp. Then, apply approximately 1.5-2 bar of pressure using a compressor. If the system cannot hold this pressure, you have a leak somewhere in the system or, worst case scenario, within the intercooler itself.
If this doesn't help, you will need to obtain the diagnostic software so that we can assist you further.

I can only confirm that.

Take a close look at the turbocharger boost hoses.
I've experienced that problem before. In the lower...
"Normal speed, then gradually increasing."
As the speed increases, you'll hear a hissing sound and see black smoke.

It was the boost hose from the turbocharger in my case.
regarding the intercooler. It has a direct connection at the outlet.
I also noticed a tear (about 3 cm long) only on the second one.
looked at, seen.

Yes, thank you for the tips!

I'll go to my workshop tomorrow and take a bicycle inner tube with me... Then I'll check each individual pipe. If it's the intercooler (LLK), then I'll have a problem, and it will be expensive. I've had problems before with the hose directly behind the turbo that leads to the intercooler.

I hope I can find some cheap underwear somewhere...
Post again when you've fixed the problem.

Thank you for the helpful tips.



Regards,

Marv.

Marv wrote:

I'm selling a Skoda Fabia (originally with engine code KBST: ATD), converted to an ARL engine with a 6-speed gearbox and all necessary components.

Hi,

Sure, here's the translation:

"Just a quick question on the side:"

What type of motor oil do you use in your Fabia?
I'm racking my brain trying to figure out how to fit a large aftermarket exhaust system into the sister model, the Polo (9N).

Regarding your problem, I also suspect a leak somewhere in the intake manifold area.
possibly a "mismatch" or "misalignment" in the control of the charging system and the EGR (Exhaust Gas Recirculation) -> 2nd post in https://community.dieselschrauber.org/en/viewtopic.php?t=10246.

@ Ulf


I installed the large liquid cooling system from ARL. It was a real pain to get it fitted, but I managed. However, the front panel had to be completely reworked. Also, we installed the liquid cooling system at an angle. Otherwise, it wouldn't have fit in terms of length.

I have the complete renovation as a photo documentary!

But I'm just wondering why you want to install that large radiator? It doesn't really bring any performance gains...


Best regards, Marv.

Marv wrote:

I have the complete renovation as a photo documentary!!!

Wow, that looks great! Could I see them? (Please send me a private message or email to [email protected]).

Quote:

But I'm just wondering why you want to install that large LLK? It doesn't really bring any performance gains...

Not directly, but it improves the thermal health of my engine. I'm running with ~160 horsepower, but still have the small ASZ-SMIC -> LLT setup, which pushes temperatures up to over 50K above ambient temperature, meaning 80°C or more in the peak of summer, even with the cooling air intake fully open .

Have you ever logged your LLT (Low Level Temperature) in the Pmax range (and subtracted the outside temperature)?

Sure, I'd be happy to send it over to you... no problem at all.


Okay, I'm using a WAES injection system (water/methanol) to reduce the intake air temperature.
The engine is essentially being tricked into thinking it has a massive intercooler, which significantly affects its performance. I might even have an intake air temperature of 40°C (104°F) even in the height of summer!
If you want more information about it: www.Turbotuning.net (This is not an advertisement ).
By the way, I also made a short video.
Sure, here's the translation:

'It was only taken with a phone camera, but you can still see how much power is packed into that car. If you want, I can send you the video.'



Best regards, Marv.

Marv wrote:

Yes, I'd be happy to send them to you... no problem.

Thank you.

Quote:

By the way, I also made a short video. Although it's just with the phone camera, you can really see the performance that's in this car. If you want, I can send you that with...

No thanks, I don't need that. A decent aftermarket cooling system is enough for my needs.

Hello,


We just checked the pressure pipe system in my workshop.
The connecting pipe from the low-pressure coolant (LLK) upwards towards the EGR is completely leaky. You can't see anything wrong; there's no oil leak, no crack, etc. But it starts leaking at just 0.5 bar of pressure.

Thank you very much to all of you for the idea of HOW we could check it. Without the bicycle inner tube and air pump, we would NEVER have found it! }



Best regards from Marv!

Marv wrote:

The connecting pipe from the low-pressure coolant circuit (LLK) to the EGR valve is completely leaky. You can't see anything wrong; there's no oil leak, no crack, etc. But it starts leaking at just 0.5 bar of pressure.

It's great that you found the problem before the turbocharger failed.
It's a shame that the immediate location tracking didn't work because of an oil leak .

Is the entire rest of your intake manifold area also dry?
Or how far up the pipe do you see an oil film on the inside walls?

Hi,


@ulf



Well, the inner tube is already lubricated with oil. However, since there's also dirt from the installation on the outside, it's not noticeable. What's curious about this is that the heat seam behind the sensor (pressure sensor? I'm not sure exactly) is sealed. Behind that is a mounting piece. Apparently, the air is finding its way in under that seam. Even the workshop was very surprised.


I'm already so enthusiastic about those great Clip Fix connections... That's the last cough!
Do you happen to know of any companies that offer adapter flanges for the VW system?

I've already contacted Grundler, but I'm not satisfied with their customer service.
They don't respond to phone calls, nor do they answer email inquiries.

I'd like to do some more work on the intercooler system during the winter break.





Best, Marv.