"Fast idle" is a symptom, not a thing that can be replaced. Could you be referring to the Automatic Idle Speed (AIS) motor being replaced a couple of years ago?
The raw fuel smell suggests a sensor problem, most commonly the MAP sensor. It reads engine vacuum to determine load on the engine. More load requires more fuel. There are two different possibilities with this type of sensor. At first it can report incorrect readings that are within the limits of normal operation. The engine computer will believe the sensor and command extra fuel to be delivered. Second, when the sensor gets worse and reports readings that are outside specific design limits, the engine computer will know that sensor can not be trusted. It will disregard the sensor, inject an approximate, calculated value based on other criteria, memorize a diagnostic fault code in the engine computer, and the computer will turn on the "Check Engine" light to let you know an emissions-related problem has been detected. Due to that injected, calculated value, it's not unheard of for the engine to actually run rather well, but the clue is the Check Engine is on.
If your Check Engine light is on, there is a diagnostic fault code that will lead you to the circuit with the problem. Do not disconnect the battery until the code(s) has been recorded or that valuable information will be lost.
Tuesday, December 8th, 2009 AT 2:56 AM