04 STI Misfiring
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This is a discussion on 04 STI Misfiring within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hello, this is my first post on these forums and I come bearing some problems. The other day, I was ...

  1. #1
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    04 STI Misfiring

    Hello, this is my first post on these forums and I come bearing some problems. The other day, I was driving home from work, and then tried to get around someone, so I kind of stepped on it.
    I heard this weird noise, and then when I hit a stop light, it was idleing very low and making a very low pitched engine grumble out the exhaust. I called a mechanic that I know, and he thought it was a cylinder misfire. I went to his house, and noticed that when I would get up higher in RPM's, the CEL would start to blink at me. He proceeded to plug in a device to check the engine, he said that it was cylinder #2 misfiring. After some time, I called around asking for 2 parts, which the mechanic suggested. A coil pack/ignition coil and a new spark plug. I thought it was kind of weird, because I had changed my spark plugs somewhat recently. (Maybe about a month or two) So, I go out and grab those 2 for about $127 and with some of his advice, I removed the battery and windshield wiper fluid container. I also had to remove some kind of piece of metal that was holding these tubes down. I proceeded to remove the coil pack and then the plug, which was surprisingly annoying.. Had to have the ratchet at just enough of a weird angle, it wouldn't seat properly on the plug.. Anyways.. I finally got them both out, and then replaced them both (Coil pack and Spark Plug [NGK]). Turned the car on, and voila! It was running again, and almost felt smoother than before between shifts. (Could be in my head) Leaving work yesterday, (this rarely happens anymore) a guy was kind of racing with me a little bit. I got on it a quite a few times, everything seemed fine. Then it makes a weird noise in one of our final runs, I let off before it got worse, and thought I saw the CEL blinking in the corner of my eye. It wasn't blinking when I revved it when I got home, and I thought it was going to possibly give me troubles the next morning.. I was correct, this morning. I was halfway to work, and the car started to feel fluttery.. Like it was losing power, then getting it back. The RPM gauge was fluttering up and down with it. Finally, when I am about to work at a stop light. I start driving and it sounds like it did the other day when it was misfiring. I kind of don't understand how.. Replacing those parts made it work temporarily, and now I am back to square one. As the title says.. This is a 2004 STI. It is a 2.5L and has a 4-inch downpipe, unknown exhaust, no other mods that I know of.. Any help would be appreciated. Also, I don't have a COBB AP, so I can't get the codes on demand.

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  3. #2
    Registered User Obeisance's Avatar
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    You mention exhaust mods but don't mention an ECU retune. Has the car been properly tuned for your more freely flowing exhaust?

    IF YOU HAVE A MISFIRE CODE ,PLEASE READ THIS!!!
    David - '05 WRX

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    That is because the exhaust mods were already there. I have done absolutely nothing to the car except replace some stuff. (i.e brakes, rotors, etc.) As far as tuning goes, I am completely in the dark. I have read over all those basic checks before I posted this. I am wanting to be very thourough in how I approuch this, and provide some back story of what happened. When I think about it, it just seems like it would be the injectors. In the past, I have gotten on it and at about 140 mph, the car just shut off. Which could be insufficient fuel getting through the injectors.
    Last edited by Shipyard; 01-24-2014 at 07:34 AM.

  5. #4
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    Also, this morning, when it was sitting idle, it idled normal, then went extremely low, then normal again.

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