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P0304 not a coil or plug issue.

Old 01-01-2019, 12:59 PM
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Scott Heit
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Default P0304 not a coil or plug issue.

Hello all!

I am getting a P0304 misfire cylinder 4 on my 2003 Boxster base. This ONLY happens when I floor it from standstill or floor it from lower speeds. If I floor it while already at higher speeds it does not occur. The coils and plugs are less then 1 year old and I swapped the coil and plugs between cylinder 4 and cylinder 1 and the problem did not move.

What any you oh wise ones? Injector? Cat going bad? Thanks in advance for any help.

- Scott
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Old 01-01-2019, 02:04 PM
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Default Update

Added some Techron to the gas tank. Drove around awhile to get engine nice and hot. Still getting code flashing but now it doesnt stay on for me to check if it is still P0304. From flooring it the light flashes between 90-100 mph then goes out. Interesting... perhaps a few more Techon treatments and it will go away?
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Old 01-01-2019, 02:13 PM
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996AE
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Swap injectors if the Techron doesnt clear it up.

Also check spark plug gap and double check coil click stap in plug is seated.
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Old 01-01-2019, 02:20 PM
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Scott Heit
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Default Side note

Side note...my 2003 does not have spark plug tubes so it's not that.
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Old 01-01-2019, 02:21 PM
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Default Thank you

Originally Posted by 996AE View Post
Swap injectors if the Techron doesnt clear it up.

Also check spark plug gap and double check coil click stap in plug is seated.
Thank you. Will do and report back as I drive it more, likely tomorrow.
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Old 01-01-2019, 11:52 PM
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Check the coil packs for cracks. Ignore this, you already check for that, Can't delete the response.
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Old 01-02-2019, 12:42 PM
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Scott Heit
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Default Update

Forgot to also mention it is a Tiptronic. Anyway update after today's drive of 50 miles:

Flooring it from standstill or lower speeds still turns on the flashing engine light. It's consistently between 90-100 when it flashes. If I keep it floored and go over 100 it goes away. If I slow down below 90 it goes away. If I keep it in the 90-100 range with it flashing it will go solid and with the P0304 misfire cylinder 4 code.

Next fill up I will do another bottle of Techron. After that it's on to checking or swapping the injector.
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