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P0303. Need help

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Old Oct 30, 2025 | 06:14 PM
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Default P0303. Need help

P0303 code, only misses below 1000 rpm. Plugs, wires, coil injectors and head have been replaced. Any suggestions, dealer is talking about replacing the engine which will end the warranty
2007 jkur.
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Old Oct 31, 2025 | 03:33 AM
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With all the parts that have been thrown at that, has the wiring harness and connector at the sensor(s) been checked?

Swapped coil pack to another cylinder with no issue to see if it is bad and fires the code on the new cylinder?

This is the 3.8, correct? All the rockers are good? Compression test is good I am assuming?

Has it been put on a scope to check the injector pulses and cam signals?

I am more familiar with the 3.6, but some of the troubleshooting may be the same and yield some answers.
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Old Nov 1, 2025 | 07:55 AM
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Originally Posted by IIQII
With all the parts that have been thrown at that, has the wiring harness and connector at the sensor(s) been checked?

Swapped coil pack to another cylinder with no issue to see if it is bad and fires the code on the new cylinder?

This is the 3.8, correct? All the rockers are good? Compression test is good I am assuming?

Has it been put on a scope to check the injector pulses and cam signals?

I am more familiar with the 3.6, but some of the troubleshooting may be the same and yield some answers.
Yes 3.8L, compression was good dealer said leak down was 30%. I did a leak down and got 10%. The coil was replaced with a new Mopar coil. The dealer now says the replacement he’s was defective and they are replacing it again.
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