What could cause my idling to go up to 3000-4000 rpm's in neutral?
Aug 25, 2017 at 9:27 AM
Fast idle in neutral
BALBAUGH
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I would suspect either a bad idle air control valve or a vacuum leak (specifically the intake manifold gasket) if there is no service engine light. If there is a light, get it scanned and let us know what the code(s) it has. You can get that done at the local auto parts shop.
Guide on how to check for vac leaks: https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
Guide on idle air control (IAC) valves: https://www.2carpros.com/articles/how-a-idle-air-control-valve-works
How to replace an IAC valve: https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac
Guide on how to check for vac leaks: https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
Guide on idle air control (IAC) valves: https://www.2carpros.com/articles/how-a-idle-air-control-valve-works
How to replace an IAC valve: https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac
Aug 25, 2017 at 11:43 AM
And then I found this. It could be caused by a bad connection at the throttle position sensor. Here is the service bulletin released by Mazda.
Images (Click to enlarge)
Aug 25, 2017 at 11:53 AM
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