Q: Q: Idle

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I been having problems with my idle when I give it gas in park or neutral and let off gas it will rev up to about 4 rpms and come down slow. I recently changed iac valve same thing, but when I disconnect the iac it doesn’t do it. Does this mean the new iac isn’t good or something else

A faulty or blown fuse in other electronically controlled systems can cause the IAC motor to malfunction, leading to a higher than normal engine idle speed. Other possible causes of a high idle include vacuum leaks, a malfunctioning throttle (throttle plate could be sticking; throttle position sensor could be faulty) and, rarely, a PCM/ECM malfunction. With regard to vacuum leaks, on a fuel injected engine a vacuum leak will cause a high engine idle as the engine’s oxygen sensor detect the extra oxygen entering the engine through the vacuum leak. The newly lean (too much air relative to fuel) status will result in the engine’s computer pumping in additional fuel, resulting in an abnormally high idle. If you desire that this high idle problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine idle speed diagnostic - high idle and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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