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It sounds like the IAC valve which is very easy to change on the 97-98 models but first check to see if there is a vacuum leak. Hope this helps. The IAC is the Idle Air Control valve and is on top of the intake manifold driver's side.

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โˆ™ 2007-05-08 13:33:57
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Q: What does it mean when a 1998 mark VIII is idle and the rpm's jump erratically up and down?
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