Why Does It Missfire!
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This is a discussion on Why Does It Missfire! within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; just got an 06 Sti from a local guy/friend but i'm haveing one killer issue. When ever the car gets ...

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    Why Does It Missfire!

    just got an 06 Sti from a local guy/friend

    but i'm haveing one killer issue.

    When ever the car gets "hot" say stuck in traffic for a sec or driving for a long while it gets this WICKED misfire.

    its throwing misfire codes from all the cylinders and at totally random times across those 4.

    i don't know if all the coil packs are going to **** or what!?

    I've tried 2 pairs of spark plugs (1 stock set, 1 one-step colder) as well as adding in plenty of die-electric grease.

    i just put a fresh tank of 93oct in it and no fix there either.

    the car does have 2 busted mounts from the guy who drove it last, before i got it that is

    the drive side motor mount and anti pitch mount are gone. i'm replacing them all with group N equipment tomorrow after work.

    (he must have beat the **** out of it)

    I'm stumped by this dam car, any one have any ideas?

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    He simply abides. SD_GR's Avatar
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    What flywheel are you using? Other mods? Compression? Is the timing belt on correctly or has it jumped a tooth?
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    Quote Originally Posted by SD_GR View Post
    What flywheel are you using? Other mods? Compression? Is the timing belt on correctly or has it jumped a tooth?
    the cars got an twin plate excedy carbon-carbon clutch with there lightweight flyweel, its NEVER acted like this before.

    as for the timing belt i have no idea how to check for that issue.

    it seems to me that if the engines timing was off it would act weird all all ECT's

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    Resident meany-rator 06wrx4me's Avatar
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    does it have a BOV? Is their computer tuning on it? Does it have a MBC?
    2014 Ford Fiesta ST

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    Quote Originally Posted by 06wrx4me View Post
    does it have a BOV? Is their computer tuning on it? Does it have a MBC?
    its got the stock re-circ valve on it.

    only tune on the car is to disable the rear 02cel from the cat-back and down pipe

    no MBC

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    Quote Originally Posted by 06lack View Post
    its got the stock re-circ valve on it.

    only tune on the car is to disable the rear 02cel from the cat-back and down pipe

    no MBC
    You have a DP and no engine management? Thats your problem. Get a tune, you are leaning out and misfiring.
    2014 Ford Fiesta ST

    06 WRX, HAWKEYE # 001 <T-boned and sold>

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    Quote Originally Posted by 06wrx4me View Post
    You have a DP and no engine management? Thats your problem. Get a tune, you are leaning out and misfiring.
    then why is this only happening now? (after 35k)

    and why no engine lean code?

    (dont think i'm being a ****, just asking a question)

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    Resident meany-rator 06wrx4me's Avatar
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    Quote Originally Posted by 06lack View Post
    then why is this only happening now? (after 35k)

    and why no engine lean code?

    (dont think i'm being a ****, just asking a question)
    dunno maybe your fuel filter is clogged and its making it worse.
    2014 Ford Fiesta ST

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    Does the intake look stock? Especially if it is oiled clean the MAF. It is a very easy place to start. Also any leak between the MAF and the turbo can be a problem. The turbo will suck in air and cause a lean condition. After that I would look at the fuel filter, again just because its cheap and easy.
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    Quote Originally Posted by mycologist View Post
    Does the intake look stock? Especially if it is oiled clean the MAF. It is a very easy place to start. Also any leak between the MAF and the turbo can be a problem. The turbo will suck in air and cause a lean condition. After that I would look at the fuel filter, again just because its cheap and easy.
    it is a stock intake, that much i do know

    also, i'll check the maf again but i do know the turbo intake pipeing is tight, as i just checked it tonight.

    question tho...if it was maf, wouldn't it be an issue at all ECTs?

    i cant think of any maf table i've ever seen that ties into ECT....

    thanks guys.

    also, where is the fuel filter located?

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    Quote Originally Posted by armysti View Post
    thanks!

    i'll swap that tomorrow as well.

    any other ideas guys?

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    Quote Originally Posted by 06lack View Post
    it is a stock intake, that much i do know

    also, i'll check the maf again but i do know the turbo intake pipeing is tight, as i just checked it tonight.

    question tho...if it was maf, wouldn't it be an issue at all ECTs?

    i cant think of any maf table i've ever seen that ties into ECT....

    thanks guys.

    also, where is the fuel filter located?
    I really have no clue what ECTs are. I can't find anything searching either. Are you talking about the external temperature? Heat soak will exacerbate the issue because of the charge temperature.

    Next thing I would do is take off the intercooler and see if it is full of oil. It will also cause misfires. There should only be a little in there at most. See if the throttle body is clean while your in there.
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

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    Quote Originally Posted by mycologist View Post
    I really have no clue what ECTs are. I can't find anything searching either. Are you talking about the external temperature? Heat soak will exacerbate the issue because of the charge temperature.

    Next thing I would do is take off the intercooler and see if it is full of oil. It will also cause misfires. There should only be a little in there at most. See if the throttle body is clean while your in there.
    sry....ECT= Engine coolant temp

    when i do the mounts tomorrow i'll have the IC off and i'll check for oil and general dirt.

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    Admiral Ackbar the 1st mycologist's Avatar
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    I did a lot of searching and got some good advice when I had audible ping not too long ago. Here is a list of possibilities pasted from my thread. Engine managment would be a very good consideration for you and you could do some logs, they might help.

    Results from searches:

    1)Cobb map is conservative, runs rich. Should be trusted.
    or (take your pick on the thread)
    Cobb map is actually leaner than stock - never heard of anyone running Cali 91 map on 93 octane, but is a possibility.



    2) PCV valve - should be changed every 15K miles, or never (take your pick). Mine was fine.

    2.a) Oil catch can - not done.

    3) Turbo oil seals shot - seems not. No oil in downpipe, not much in intercooler

    4) Engine deposits - can cause preignition as well, or increase compression and otherwise cause spark knock (at issue here). Finishing 1st tank with synpower cleaner.

    5) Spark plugs - do show signs of detonation (metal balls stuck to ceter electrode). Plugs replaced with OEM gapped to .028 (yesterday, not tested hard yet).

    6) Blow by - oil in intake, reduces octane. Check compression.

    7) Elevation - Colorado people say 91 octane = 93 octane there, should be a safeguard
    or
    Need higher octane at high elevation (web auto professionals and occasional threads)

    8) Boost - peaks at 15.8 settles at 15 then tapers. Compensation map in ECU reduces peak boost by 1 PSI per ~3500' IIRC, so normal stage II numbers.

    9) Vacuum issues (haven't figured out how to check system yet).

    10) Injectors plugged, tired, or imbalanced (40K miles, always top tier gas, never cleaned). Unlikely - all four cylinders are affected.

    11) MAF or Temp sensor problem.

    12) Dealer - go parade my just installed stage II setup and void my warranty on a totally unabused motor with a potentially bad ring land. Get unheard of and unreported "ping" reflash that was never mentioned when I was there complaining about ping.

    13) Knock Sensor? Don't know how to test that.

    14) Head gasket??? I guess I should add this because I have had to burp the coolant a few times recently. I had a small coolant leak from a line a while back but it was supposedly corrected/pressure tested at the dealer. The system was then flushed at 30K (dealer) and there has never been any indication of overheating.
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

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