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2004 gto serious problem

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Old Sep 21, 2016 | 06:26 PM
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Default 2004 gto serious problem

Hi there im new to this site and ive been looking at old posts all day and nobody seems to have my problem so sorry for making a new thread that may have been answered and gone over sometime on this forum in the past.So here it goes i have a 2004 gto with a mystery problem.The cel is on alot and even flashes sometimes indicating a misfire which I know is really bad.the thing is when im on the freeway it runs really smooth like normal and the cel will eventually turn off by itself no scaner tool required.But when i sit in traffic and sit at a red light the idle gets really rough and it throws the code agin.mpg is really bad when the cel is on and its not idling smoothy at all it stinks like gas to.As soon as you start moving agin it smooths out.the problem has been getting worse and worse i took it to a friends shop and he put new spark plugs checked all my coil packs and i even had him tighten the intake mani down to its proper torque settings,i also cleaned my maf.the crazy thing is it even runs smooth and clears the code around town somtimes like it runs like new agin but sitting always makes it come back faster.Basically if i stay on the freeway the code takes really long to come back its like a low rpm problem.Ive just about run out of ideas and money to keep trying to fix it ive had 3 ls1 powered cars never had any engine trouble until this gto. The mileage is 98000 and its bone stock nothing done to it at all.I scaned the code and it says running lean and my mechanic says that doesn't help because that could b many things.i also had a smoke test done on it and theres no leaks!wtf!Some one please help me out here im stumped n **** outta ideas.
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Old Sep 21, 2016 | 06:32 PM
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I had this problem on a 2002 Tahoe and it ended being the wire harness on passenger side coil pack.
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Old Sep 21, 2016 | 06:59 PM
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Wire harness on passenger side coil pack?were is this located?
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Old Sep 21, 2016 | 07:00 PM
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Was it visibly damaged r just internal?
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Old Sep 21, 2016 | 08:21 PM
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It's the harness that connects the four coils into the single connector. I could not see the damage on mine but I didn't dig too deep as engine was running perfect with new harness
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Old Sep 21, 2016 | 08:25 PM
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Ok thanks ill go check that
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Old Sep 21, 2016 | 10:19 PM
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Just to be clear, the driver side also ha it's own harness for the four coils on that side. If I remember correctly I got a p0354 code when this happened which led me to the passenger side coil harness.
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