Car has only 100K on it, a very low mileage 300E. I put in Autolite 104's, which is a non-resistor plug that many other W124 owners are having good success with. (I realize the spec plug is a Bosch H9DC). The plugs I replaced were only in for about 10K, and they were HR9DC, the resistor version. The wires are Bosch wires that seem of very high qaulity and are custom fit for this car.

What is a good way to check fuel pressure? At the injectors? Any other details would be appreciated.

Just filled up and am getting 13 MPG and the motor's power is way down.

By the way, figured out the clicking in the door and looping at idle (the more minor of the two issues I reported). It turns out that the driver window switch was being pushed down because the wood paneling at the console was not put back in properly (by me) and was actually pushing one side of the switch down. So the clicking was coming from the motor or lifter inside the door. Reinstalled the trim properly and that problem is solved. The 5-7 second looping is gone.

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Treiberg's Collection: 1981 240D, 1985 300SD, 1992 300E, 1997 E300D, 2005 C230K