Let's see - car running OK, but having high idle issue ... mechanic changes plug wires and it won't run hardly at all ... I've done this at least three times myself over the years ... greatest likelihood is wires no longer going to correct cylinders, or, more than one wire is bad ... I like the first one better ...

I have had one bad wire in 30 years (after 100K on a late model Chrysler), no completely bad plugs ever ... and three times of screwing up the wire to plugs order ...

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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg