Code P0304

2000 MITSUBISHI ECLIPSE
245,000 MILES • 3.0L • V6 • 2WD • AUTOMATIC
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2000MITSUBISHI GT
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Hi, I recently bought the car listed above. I am using it as a project so I can know more about cars inside and out. One code keeps popping up that is P0304 cylinder four misfire. So far I replaced all spark plugs all spark plugs wiring, idle air control system, distributor cap and rotor. I changed my oil to full synthetic using now premium 91 gas. But the check engine light keeps popping up as fourth cylinder misfire! So now am stuck an do not really know what is the next diagnosis or step to fix the problem. Can anyone help me?
Mar 5, 2018 at 6:50 PM
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MHPAUTOS
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Check compression at that cylinder and check for a vacuum leak at the inlet manifold around number four cylinder, start here.
Mar 6, 2018 at 12:38 AM
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RENEE L
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Hello 2000MITSUBISHI GT,

I am sending you a link to an article from this site on how to conduct a compression test. This article contains written step by step instructions with pictures and two videos. One of the videos shows you how to conduct the test with a gauge and the other shows you how to conduct the compression without a gauge.

https://www.2carpros.com/articles/how-to-test-engine-compression

If you have any further questions please return to this post. We are always happy to help.

Kindest regards,

Renee
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Mar 6, 2018 at 1:26 PM
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2000MITSUBISHI GT
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Hello thank you guys for the help, now I’m looking to change my fuel filter but having trouble locating the filter itself. Where would I first look?
Mar 9, 2018 at 12:42 PM
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MHPAUTOS
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  • 31,937 POSTS
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It is an in line filter, just follow the fuel lines and you will see it, i do not have an exact location, if under the car it may have a cover over it,
Mar 9, 2018 at 4:41 PM
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