First when dealing with a rough idle you must look at everything . How is the c/o? Did they perform a compression test, cylinder leakage test? Did they perform a fuel distributor test. 50% of rough idles end up being ignition related, 20% fuel and the other 30% is mechanically related due to burned valves or even c/o not in spec. (lean mixture) . I have dealt with some rough idles that will make you cry, but performing the proper procedures for diagnosis is essential. It saves you (the customer ) money and me (the technician ) from looking like a fool for throwing parts at you car.. Just my 2 cents not meaning to offend anyone.

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euro 287
Mercedes Technician 7 Years (retired to Hyundai)
2000 Dodge Durango
98 Mazda truck