Is the clutch bad? If it does't always work you might want to check the air gap. I just made a clutch repair to my Ford. The air gap had increased to .048and it needs to be .015. It was a easy repair on the Ford. Remove the face plate and remove shims as needed. No tool required just a flat stock across the face to loosen the center bolt.

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2009 CLS550 55,000
2004 ML350 144,000
2004 X5 95,000
2002 X5 165,000
1996 320S 155,000 (sold)
1991 190E 192,000 (sold)
1989 300SE 160,00 (sold)
1984 300D 210,000 owned since 85, (sold)
1984 300SD 160,000 (sold)