# Is this a normal noise at idle when AC is on? **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** civic, engines, honda\ **Created:** [June 28, 2023, 12:46am UTC](https://community.cartalk.com/t/is-this-a-normal-noise-at-idle-when-ac-is-on/191352 "2023-06-28T00:46:40Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![JayZeeBee](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/jayzeebee/32/31532_2.png) [@JayZeeBee](https://community.cartalk.com/u/JayZeeBee)\ **Post date:** [June 28, 2023, 12:46am UTC](https://community.cartalk.com/t/is-this-a-normal-noise-at-idle-when-ac-is-on/191352/1 "2023-06-28T00:46:40Z")
Preface - I have anxiety specific to my car breaking down which makes it hard for me to tell the difference between “normal” car noises and those that are indicative of a problem. When my AC is on, periodically when my car is at idle there will be a brief shudder. I also notice it when I put my car in reverse. It will also occasionally vibrate a bit at idle with AC off, but I notice it most when my AC is. It is not frequent enough that I could take it to a mechanic and reproduce it. Usually it is after the car has been running for a bit (5-10 min). I wouldn’t mind it so much but recently my engine misfired and died, ~60 mph. It got a new set of plugs and coils and now seems to run smoother. But if there is a problem that is indicative of a larger issue, I want to take care of it. It’s a pretty old car… 2008 Civic, 189k thanks! ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [June 28, 2023, 1:11am UTC](https://community.cartalk.com/t/is-this-a-normal-noise-at-idle-when-ac-is-on/191352/2 "2023-06-28T01:11:26Z")
Have you tried cleaning the electronic throttle body? ![image](https://global.discourse-cdn.com/cartalk/original/3X/6/3/63ac85a220cc040287cebb83b7810572a63285da.jpeg) This is what controls how the engine idles under different load conditions. The engine misfiring and dying at speed is a different problem. And sometimes that’s caused by a faulty crank sensor. > **[Bad Crankshaft Position Sensor Symptoms & Problems](https://www.1aauto.com/content/articles/bad-or-failing-crankshaft-position-sensor-symptoms)** > > Problems with the crankshaft sensor will often present as problems with engine timing. If you think your sensor has failed, here are some common symptoms of a bad crankshaft sensor that can help you in determining whether or not it has failed. Tester ---
**Author:** ![eddo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/eddo/32/2594_2.png) [@eddo](https://community.cartalk.com/u/eddo)\ **Post date:** [June 28, 2023, 5:50pm UTC](https://community.cartalk.com/t/is-this-a-normal-noise-at-idle-when-ac-is-on/191352/3 "2023-06-28T17:50:25Z")
take it to a trusted mechanic for a complete look over and inspection. This could be motor mounts that are worn, a dirty throttle body like Tester suggested, or a vacuum leak of some kind. Some things can be figured out with out the symptoms being present. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [June 29, 2023, 9:34pm UTC](https://community.cartalk.com/t/is-this-a-normal-noise-at-idle-when-ac-is-on/191352/4 "2023-06-29T21:34:06Z")
It could be an overactive imagination, like you say. I had a late 70’s VW Rabbit years ago. Part of the routine maintenance was removing & checking the fuel injector spray pattern. First time I did this, heard a very high pitched noise from the injector when it sprayed. Ever after doing that job, I could hear the injectors’ high pitched tone as I drove, esp when accelerating. But I never heard it before doing that job, although it was certainly always there from day 1. ---
**Author:** ![JayZeeBee](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/jayzeebee/32/31532_2.png) [@JayZeeBee](https://community.cartalk.com/u/JayZeeBee)\ **Post date:** [July 1, 2023, 11:37pm UTC](https://community.cartalk.com/t/is-this-a-normal-noise-at-idle-when-ac-is-on/191352/5 "2023-07-01T23:37:21Z")
I have not. I will investigate that. Thanks! ---
**Author:** ![JayZeeBee](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/jayzeebee/32/31532_2.png) [@JayZeeBee](https://community.cartalk.com/u/JayZeeBee)\ **Post date:** [July 1, 2023, 11:37pm UTC](https://community.cartalk.com/t/is-this-a-normal-noise-at-idle-when-ac-is-on/191352/6 "2023-07-01T23:37:59Z")
Ok, thanks for your thoughts. PA inspection is due soon anyway.