stuttering 06 STi
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This is a discussion on stuttering 06 STi within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; ok so here is my situation hopefully someone has something helpful. i traded in my 03 WRX for an 06 ...

  1. #1
    Registered User bullmonkey118's Avatar
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    stuttering 06 STi

    ok so here is my situation hopefully someone has something helpful. i traded in my 03 WRX for an 06 STi. but the STi i currently have was modded by someone else.(might i mention if you traded in a black STi with gold rims and it said precision tuning on the windshield in lakewood new jersey you are an absolute moron and need to stick with old muscle cars that don't mind being rigged in ways that don't make sense.) mods include an APS front mount intercooler and cold air intake, perrin turbo inlet, 3 inch down pipe, and a manual boost controller. i do not have a check engine light on but i am getting some rough idling and some bogging down, stuttering, or chugging whatever you want to call it but on the freeway cruising it is incredibly annoying. i changed the pcv valve and it seemed to have fixed my gas mileage problem and the car ran very smooth for about a day but is now actually acting up worse than before much more defined. anyone that has had this problem fixed would be a great help. i had a z24 cavalier that did this once and the coil packs were the problem but i don't know if i can part with 240-400 dollars on an educated guess before i ask other people.

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    Registered User lordcon's Avatar
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    Obvious problems:

    1) manual boost controller - you need to take this off. It is the devil. Boost is managed by the ECU on our cars and it doesn't like to be overridden.

    2) Front mounted intercooler is going to cause serious engine response issues if the car is not tuned for it.

    3) Again, an intake (especially a cold air) on these cars without being tuned will cause the problems you are describing. Revert back to stock.

    4) stock turbo? You dont need a front mount. Revert back to stock if on the OEM VF-39 turbo. You are getting serious lag issues with a massive front mount on that turbo. Its inefficient.

    Personally, i would have never bought a car that was obviously modded, but whats done is done so you need to make the best of the situation. Work on getting all the stock parts for the car back on, try to find out if its been custom tuned. If you cant, think about investing in a Cobb Accessport to clear a custom map and reflash back to stock or an appropriate stage w/ mods.


    -j
    Quote Originally Posted by jeffbmx00 View Post
    nah i dont have a problem with spelling, i just play a lot of world of warcraft and thats how people type in that game.

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    Master Baiter EJ257's Avatar
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    Take it to a shop and have them tune it for you. It could've had more mods someone took off (but didn't adjust the tune)

    Quote Originally Posted by lordcon
    1) manual boost controller - you need to take this off. It is the devil. Boost is managed by the ECU on our cars and it doesn't like to be overridden.
    Fine if tuned

    Quote Originally Posted by lordcon
    4) stock turbo? You dont need a front mount. Revert back to stock if on the OEM VF-39 turbo. You are getting serious lag issues with a massive front mount on that turbo. Its inefficient.
    If properly tuned, the lag isn't awful. More timing, more boost, more power

    Quote Originally Posted by lordcon
    3) Again, an intake (especially a cold air) on these cars without being tuned will cause the problems you are describing. Revert back to stock.
    He'll need the intake with the FMIC
    Last edited by EJ257; 04-30-2009 at 04:17 AM.
    2005 WRX STi (Mods | Virtual Dyno)

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    "Never trust anything that bleeds for a week and lives ..."

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  5. #4
    Registered User lordcon's Avatar
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    Quote Originally Posted by idipskoalmint View Post

    He'll need the intake with the FMIC
    Yeah i realized that as i was typing the response. If he reverts back to a TMIC, id ditch the CAI.

    Also, some would argue that even with a tune..an APS front mount is still overkill for a vf39, intercooling could be done more efficiently. But the OP didn't identify what turbo is in the car...so its speculation on my part.
    Quote Originally Posted by jeffbmx00 View Post
    nah i dont have a problem with spelling, i just play a lot of world of warcraft and thats how people type in that game.

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by lordcon
    Also, some would argue that even with a tune..an APS front mount is still overkill for a vf39, intercooling could be done more efficiently. But the OP didn't identify what turbo is in the car...so its speculation on my part.
    It is overkill, and I would not recommend someone spend $1000+ on a FMIC for their stock turbo unless they're trying to get into OEM turbo records or anything. However, he already has it (the APS unit is pretty good), and the FMIC will allow you to increase the timing and the amount of boost you're running. If he were to swap for the OEM top-mount, he'd still need to get a tune.
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning, LLC

    "Never trust anything that bleeds for a week and lives ..."

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    Registered User bullmonkey118's Avatar
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    i'm not going to lie i was giving serious consideration to going completely back to stock on this car until i heard that people had this problem with bone stock cars. and surprisingly i reach full boost around 3000rpms so i wouldn't say thats a whole lot of lag. i can't guarantee its the stock turbo but it looks like it. i would also like to upgrade some things too like change the turbo the injectors and the fuel pump and at that point the add ones that are already there will be nice once tuned, but i could end up like other people that that had this problem figured they would upgrade their cars and still had this problem. i have read stories of people replacing their ecu their coil packs and spark plugs and their wire harnesses and still didnt fix it, i'm just hoping someone out there had this same problem and actually got it fixed. i have only read one that was going to change the ecu after the dealer told him that the ecu stopped sending the #1 coil pack a signal at low rpms but there were no more threads after that one.

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    Registered User lordcon's Avatar
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    If you are going to upgrade the turbo, then the setup you have is fine...as long as you are tuned for it. It sounds to me like the previous owner probably had some other turbo setup on it and then went halfway back to stock when he traded the car in. Thats the only explanation i can think of for it having an APS front mount on the car, anybody who does even a little bit of research should have realized that it would have been total overkill on a stock setup.

    Id bet money that the problems you are experiencing are because of an aftermarket intake, front mount intercooler and a manual boost controller without a tune.

    As i see it you have two routes to fix the problem. Upgrade more parts and get tuned, or go back to stock. Upgrading and a tune will cost you more, but it all depends on what your goals for the car are.
    Quote Originally Posted by jeffbmx00 View Post
    nah i dont have a problem with spelling, i just play a lot of world of warcraft and thats how people type in that game.

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    Registered User bullmonkey118's Avatar
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    that all sounds dead on, the only thing that gets me is it really runs terrible in low rpms and when cruisin but is smooth and pulls hard when on the throttle. i don't doubt for a second that he pulled off some parts, and no one trades in a car for a two year newer model after putting money into the one they had if they didnt screw something up but if i'm not mistaken isn't the intercooler, the bov, and the boost controller pretty much dormant parts before the turbo boosts? if thats so then i don't know that i can blame the car running as rough as it does at low RPM's on what he did. i'm thinking when it started running like this initially he took it to his tuner, tuner couldn't figure it out because it wasn't caused by the tune or the parts and this frustrated the previous owner and made him just want to trade it in. then he took the parts he wanted to keep and discarded the car. none the less these are all valid points and if i ever get a hold of meade engineering or bring it to a dealership i will definitely mention everything you guys have pointed out and i will post what they say. thanks guys

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