Coil Packs for a 03 STI

Learner Driver
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Coil Packs for a 03 STI

Postby lscislowski » Mon Jan 29, 2018 5:39 pm

Hi Guys
Was wondering if anyone might be able to help me out with some coil pack knowledge?
I have a 2003 WRX STI Australian spec engine that I bought. Long story short, the engine was missing under boost, it had incorrect spark plugs, I have replaced the spark plugs with the correct ones, the engine will now boost to 16psi (standard boost) but sometimes has a little miss here and there under boost. The plugs made a huge difference, and I'm suspecting that I may have a problem with one of the coil packs. I'm suspecting the coil packs as I notice these are not original, they appear to have no marking on them much the same as the really cheap ebay ones. I'm looking at getting some reconditioned ones or second hand once, as I don't really want the ebay ones in there, but don't want to spend $1300 on 4 new ones from Subaru.
The problem I got, there are several different coils, FK0140, FK0186 and FK0334. FK0140 and FK0186 are easy enough to come by, and sellers claim that they both fit a 03 STI motor, but from the research I have done I know that they are different coils, one has a 3ms dwell and the other 5ms dwell. FK0140 has a Subaru part number 22433-AA421, and can also be used instead of 22433-AA560. FK0186 has a part number 22433-AA540, can also be used to replace 22433-AA418, 22433-AA480, and 22433-AA640. None of the part number cross reference between FK0140 and FK0186 so that also suggests that they are infect 2 different coils.
Now, not sure what went on a 2003 WRX STI, but I know from the dealer that the coil part number is 22433-AA551, which is different to the numbers I just listed, at a guess I believe 22433-AA551 may actually belong to FK0334. Is there anyone who has a 2003 Australian 2.0L STI that could confirm this for me or may have a bit more knowledge on the subject?
Also what is the difference with FK0334, can I use FK0140 or FK0186?

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Red Bugeye Driver
Red Bugeye Driver
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Re: Coil Packs for a 03 STI

Postby Subey » Wed Feb 07, 2018 4:38 pm

Fk0140 is from a wrx, you want fk0186 as they have a longer dwell suitable for higher boost. The ecu also has dwell time settings, so just swapping coils on a wrx won't help, you need the tune tweaked too.

No idea what fk0334 came out of, but for your gen you want fk0186.

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