The threads are probably stripped on the adjusting tube. Mine stripped on my 103 engine. For a temporary fix I loosened the tube and wedged in a small u-bolt as a spacer so it would tighten up where the threads were good. The u-bolt I am describing was the type used to secure the cable system on garage doors. I had to grind it with a Dremel to get it to fit. It is still there. I bought the new parts but haven't installed them yet.

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1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T