Hello everyone, I'm new to this forum and have already read many interesting things. Here's my first post, which aims to help those who are new to diesel engine repair by providing information on how to identify problems in the turbocharger system. I'm also a novice when it comes to the diesel sector.
After a timing belt failure on my Allroad 2.5 TDI AKE, I had the cylinder heads rebuilt with new valves, rocker arms, hydraulic lifters, etc. Subsequently, the engine was completely reassembled. However, during the first test drive, I didn't achieve the same performance as before the engine failure, even though I meticulously cleaned the heavily clogged intake manifold (air intake and cylinder heads). And all the carbon-fouled fuel injectors were cleaned and inspected.
 Then the disaster began. In the evening, it was still running with this slight loss of power - in the morning, it was only sputtering and whining, so much so that I had to end its suffering with a left turn of the key. As a result, the error memory was full! Now, the fuel injection pump was defective. So, I removed the fuel pump from my spare vehicle and used it, and I also readjusted the fuel injection timing.
After the installation, we took it for a test drive, but it didn't work. The performance was the same as before - still not sufficient. It was now...
However, there are no more errors. What now? During the diagnosis, I noticed that the control pressure for actuating the turbocharger, and of course the boost pressure itself, were too low and consistently varied in their values.
I have gradually replaced everything. Starting with the old turbocharger, then the intercooler (due to oil contamination and a suspected leak), and finally the boost pressure regulator. Of course, I also checked the entire vacuum system and the function of the variable geometry turbocharger (VTG), the exhaust gas recirculation (AGR) system, and the exhaust system. After another test drive and countless diagnostic readings, I still had no power!  
I was about to set the car on fire. Then, I did some more online research (as I had done many times before) and reviewed the charging system again that evening. Despite a verschandeln error memory, I decided, as a last resort, to replace the intake manifold pressure sensor. And now, with "rubbel-die-Katz" (presumably a nickname or term), the engine is running smoothly with a consistent boost pressure, resulting in a stable charging pressure!
Looking back, you'll see that I didn't have to replace everything, but I had to re-familiarize myself with the subject matter, as I completed my apprenticeship over 30 years ago and haven't worked in the automotive industry since.
Conclusion: If the vacuum system is functioning correctly, the intercooler system has no pressure leaks, the turbocharger and exhaust gas recirculation system are working properly (of course, the fuel injectors must not have significant variations - otherwise, you'll already have a loss of power), but still insufficient boost pressure is being generated, then you should use a diagnostic tool to check the target and actual values for the boost pressure control valve and the boost pressure itself. If there are deviations below the tolerance limits, you need to determine which component is responsible. Usually, this isn't too difficult, as the error memory can help - but that wasn't the case for me! I was ultimately trying to figure out which sensor or transducer provides data/values to the engine control unit (ECU) that are relevant to the turbocharger boost pressure.
= the intake manifold pressure sensor.
I hope that some people find my research helpful or learn from my mistakes.  🤠 Audi Allroad 2,5 TDI "AKE" Bj. 2002 |
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