I'd also consider an A/F reset: Remove negative battery terminal for 10 mins or so, then reconnect. Start engine, do not touch accelerator. Engine idle will be slightly high, and will fluctuate. The ECU will time a test 5 minutes after the engine drops out of cold-start mode. What you'll see is idle up to about 1500, then drop and stay around 1000 rpm. At the end of the test, idle will drop to 700. Now the A/F is set. Wait about 6-7 mins, and listen or check the tach for the drop.
Common vacuum leaks include the PCV vacuum line. You should be able to find a ton of information on that on here because it causes many problems in older Zetecs. Depending on how it goes bad it can cause a high or low idle.
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Originally Posted by the user formerly known as ZX3_Chick
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