For 2 years now the 744 16v has not idled right and given poor fuel mileage (24mpg). This mileage is about 10% less than I have gotten before.
The car starts and idles fine cold, but once warm (3 minutes or so) the idle is too high (1100 rpm) and is rythemically (sp?)rough. By that I mean it's as if it has a constant miss.
All plugs look fine, and once you open the throttle it runs fine. Full throttle pulls right to the redline with no hesitation or miss. The O2 sensor is reporting rich mixture (reads about 0.75 volts constant) at idle. If I remove a vacuum hose, (lean the mixture), the sensor begins oscillating as it should. So it is capable of operating correctly. I can detect the rich mixture on trailing throttle also.
I have checked the temperature sensor, it is in the normal range and the voltages on it to the ECU are correct (380 ohms hot, about 1.5 volts).
Could this be a leakning injector? I have never had anything like this so I was wondering if this was a symptom of that.
I know I can pull the injector rail, but I also dread the mess that can be with stuck injectors and old fuel lines which bend instead of loosening.

Anyway to be sure it's an injector?
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84 242Ti IPD bars&springs, 89 745 16v M46 IPD bars, 89 744 16v M46 IPD bars, 90 745 AW70, 91 245SE AW70 IPD bars, 93 245 CLassic M47