While trying to adjust the tension on the accelerator pedal (91 300D), I noticed that the white plastic part that has the thumb wheel and the screw drive is broken at the end. It's still screwed into what it's screwed into, just broken at the end, where there's a black cap.

What is this part called and is there a DYI pages somewhere to show me how to replace it?

Thanks.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife