# Help PO303 & 304 cylinder misfires

**URL:** <https://community.cartalk.com/t/help-po303-304-cylinder-misfires/150305>\
**Category:** Maintenance/Repairs\
**Created:** [October 8, 2019, 4:46pm UTC](https://community.cartalk.com/t/help-po303-304-cylinder-misfires/150305 "2019-10-08T16:46:52Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Lexi\_Hutcherson](https://avatars.discourse-cdn.com/v4/letter/l/90ced4/32.png) [@Lexi\_Hutcherson](https://community.cartalk.com/u/Lexi_Hutcherson)\
**Post date:** [October 8, 2019, 4:46pm UTC](https://community.cartalk.com/t/help-po303-304-cylinder-misfires/150305/1 "2019-10-08T16:46:52Z")

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09 Subaru Outback 4 cylinder. I replaced the spark plugs and cords and the codes went away for about a week. I have a friend who thinks its my fuel injectors but it could also be my coil. How do I tell what it is?

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**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:** [October 8, 2019, 5:16pm UTC](https://community.cartalk.com/t/help-po303-304-cylinder-misfires/150305/2 "2019-10-08T17:16:20Z")

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Swap those components to a cylinder without a miss, and see if the miss moves to those cylinders.

Tester

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**Author:** ![tcmichnorth](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tcmichnorth/32/25126_2.png) [@tcmichnorth](https://community.cartalk.com/u/tcmichnorth)\
**Post date:** [October 8, 2019, 6:03pm UTC](https://community.cartalk.com/t/help-po303-304-cylinder-misfires/150305/3 "2019-10-08T18:03:07Z")

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Swap the coils first. Then see if the misfire moves. If they don’t, then repeat with injectors.

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<div class="post-metadata">

**Author:** ![Lexi\_Hutcherson](https://avatars.discourse-cdn.com/v4/letter/l/90ced4/32.png) [@Lexi\_Hutcherson](https://community.cartalk.com/u/Lexi_Hutcherson)\
**Post date:** [October 8, 2019, 6:09pm UTC](https://community.cartalk.com/t/help-po303-304-cylinder-misfires/150305/4 "2019-10-08T18:09:11Z")

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Can that still be done with a coil pack?

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<div class="post-metadata">

**Author:** ![tcmichnorth](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tcmichnorth/32/25126_2.png) [@tcmichnorth](https://community.cartalk.com/u/tcmichnorth)\
**Post date:** [October 8, 2019, 7:33pm UTC](https://community.cartalk.com/t/help-po303-304-cylinder-misfires/150305/5 "2019-10-08T19:33:27Z")

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Thought you had coil on plug. Sorry. But you can swap wires to check them.

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**Author:** ![Drkrachel](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/drkrachel/32/17826_2.png) [@Drkrachel](https://community.cartalk.com/u/Drkrachel)\
**Post date:** [October 8, 2019, 7:38pm UTC](https://community.cartalk.com/t/help-po303-304-cylinder-misfires/150305/6 "2019-10-08T19:38:28Z")

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What kind of wires are they? I have bought new wires at autozone and they turned out to be pure junk. Lasted about a week and I had to put the old ones back on. Now I dont skimp on them.