# Subaru rough idle

**URL:** <https://community.cartalk.com/t/subaru-rough-idle/23381>\
**Category:** Maintenance/Repairs\
**Created:** [December 14, 2008, 1:19am UTC](https://community.cartalk.com/t/subaru-rough-idle/23381 "2008-12-14T01:19:04Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mcglashanr](https://avatars.discourse-cdn.com/v4/letter/m/c89c15/32.png) [@mcglashanr](https://community.cartalk.com/u/mcglashanr)\
**Post date:** [December 14, 2008, 1:19am UTC](https://community.cartalk.com/t/subaru-rough-idle/23381/1 "2008-12-14T01:19:04Z")

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I have a 2003 Subaru Outback, 78,000 miles. It idles very rough while in drive, not in neutral or park. My mechanic isn’t sure what is causing it. Any ideas?

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**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\
**Post date:** [December 14, 2008, 1:26am UTC](https://community.cartalk.com/t/subaru-rough-idle/23381/2 "2008-12-14T01:26:13Z")

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The first step is to always rule out a mechanical fault and that means a compression test.  
If the compression is good then there is not enough info provided to make a guess.  
Plugs, wires, coils, vacuum leak, faulty injector, bad mount, Check Engine Light on, codes pulled?, etc, etc, etc.