Ah, yes, knocking makes sense. The motor mounts were probably bad too, just something they found when looking, and bad mounts will make some noise more apparent. Yes, run a good cleaner, I like Techron too. Then make sure you are buying the 91 or better fuel. Yes, it is expensive, but so is your car.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red