Q: 1.6 d16y5 engine idled high like 4k so i tested the iac and that was replaced, starts&runs fine, then idles up&down when warm?Y?

asked by on February 08, 2018

Tested iac after I started it up in the morning for work and idled to 4k and then stayed at 3k for a bit then eventually idled down so that tested to be bad and was replaced, then next day it was fine, then the gauge stopped working a week later, so I tested the ECT SENSOR with my multimeter and that was bad so I replaced that and the gauge worked for like a day and now works once in a while but makes me nervous not knowing what the temp is, but now when I start the car it idles to 2k then comes down to 1500 and then once it warms up to operating temp that I can see when the temp gauge is working it starts idling up and down from 1k to 2k rpms and doesn't stop and then the gauge usually drops to nothing like the very bottom, if any other details you think could be helpful. Let me know, thank you!!!!!

My car has 106000 miles.
My car has a manual transmission.

A faulty or blown fuse in other electronically controlled systems can cause the IAC (idle air control) 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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