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Q: Car runs great driving but when stopped at light idles down like it wants to die on 2000 Infiniti QX4

Idkes in park 900 rpm drops to 600 while in gear and brake depressed and a/c on
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There are three issues that come to mind:
-Slight depression in fuel pressure
-A dirty idle air control valve
-A failed brake booster, which causes a vacuum leak

In order to resolve the issue, testing will need to be conducted to find if the vacuum booster holds vacuum, the idle air control valve should be inspected for a clogged port in the throttle body, and the fuel pressure would need to be taken at the fuel rail.
Of course, there are other issues that can cause the low idle, and again, more testing will be needed of the vehicle passes these other three likely/common failures.
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