I installed the eBay unit on the left side and took it for a test. All seemed good. The car ran fine for 100 miles. After that, it was back to limp mode and the trouble codes returned. The fault could have been that I had purchased a bad unit from eBay, both my TB's were bad or I guessed wrong and the right one had the problem. Too many variables, too many unknowns. An unsolvable equation.
For a quick check on comparing the two pots, add the tps1Low to tps2High, which is 1023. tps2Low plus tps1High equals 1027. The ideal value would be 1024. The voltage in the pots ranges from 0v to 5v and the sensor high value is 1024. So to determine the millivolts at any setting, take the number and multiply it by 4.88. This proves that the pots are working, at least at the ends of travel within a tight range.
|Bosch 0 280 750 038 Throttle Body parts|
|Bosch 0 280 750 474 Throttle Body parts|
I installed all the old parts into the new donor body first to see if they actually fit. The reinstall process was painless, except for the magnets. They are held in place by a spring clip that has to be pressed into place. I found a screwdriver worked just fine for this task. It was just a little tricky to find the right leverage point. The plastic face went on without any issues. I found it easiest to start by aligning the pot side of the face, then gently closing it. That way the motor contacts are aligned when the face is lowered. Seemed to go easier that way.
As you say new OEM throttle bodies are now unattainable (and even more worryingly so are the Motronic ECU's which are unrepairable) so this fix is going to become essential for every owner in the very near future. The peace of mind knowing the throttle bodies are both reliable and now unlikely to smoke my ECU H-bridge is a very good feeling."