Next time you're under the hood, pull back some of the armor on the wiring harness and take a look at the wiring insulation. You'll have an appreciation for why the original wiring needs to be replaced. The cost is about $1100 for the part. Many mechanics refuse to work on driveability problems unless the engine wiring harness is replaced. The same can also apply to the electronic throttle assembly (ETA), which is the official name for the idle control valve. It is located by the plastic intake.

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95 E320 Cabriolet, 169K