A few days ago I started noticing that the family VW Passat (1.9 TDI 2000 AHU engine) somehow lost power in certain situations: Accelleration from standstill was fine, but at speed, and particularly uphill, there was no power to accellerate at all.
My first thought was that the turbo was gone. (As would half my bank account.) But although I have a very limited understanding of what the turbo even does, I had the impression that it was working fine e.g. at lower speeds. Googling around, I found many descriptions of the same symptoms, and most of the suggested solutions involved various sensors being worn or broken. This made sense to me, as I got the distinct impression that the ECU made a conscious decision to cut off power (presumably based on sensory input) rather than there being a consistent e.g. mechanical failure.
Well then, time to have a look at the engine. I had previous experience with one sensor, the air intake sensor (MAF), so I zoomed on to that. Lo and behold, the wiring nearby was not looking very healty:
Apparently these wires had come in close contact with the engine block. In any case, the insulation was melted or worn off, and in several places the copper was exposed and damaged. Oil and dirt eagerly embraced it all. The wires I’m holding up above were the most affected, and went into what I suspect is some sort of injection valve (or it could be a sensor, I can’t really tell.. it wasn’t the MAF which is prominent in the picture) which was fitted around a tube going into the engine top.
Anyhow, my engine was not running properly, and I needed to do something. And this was something. So I disconnected the battery, removed the outer two pieces of air intake plastics (two screws), and went to work with the wire cutter, WD-40, and a rag:
All the while I was working, little creatures were running around interfering with my tools and whatnot.
I brought out the soldering iron and heat-shrink tubing, and applied liberally:
I’m using a dremel tool to grind off any sharp edges on the soldered wire joints, so they won’t puncture the heat shrink from inside.
I finished with a wrapping of black gaffer tape, hoping to provide extra protection against heat and wear. However, the moral of the story I think is this: This particular wire needs to go under the (black) air intake plastics as shown in the picture above, in safe distance from the hot engine block to the right. Because that’s where it was placed when I found this problem. It was probably misplaced by myself or some service mechanic sometime.
The power loss problem has not returned so far, having driven it for 30-40 minutes. I keep driving with my fingers crossed.