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Old 08-10-2022, 05:46 PM   #1
Alaaddin
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Default Car won't rev past 3.5k rpm

I have a 2004 STI with an EJ20x swap that I did not do myself.

The car has a Blouch TD05H-16gxt turbo, TGV deletes, catless up-pipe and downpipe, fuel pump hardwire, Tomei uel headers, front mount intercooler, hks bov, and an old protune on a v2 accessport.

The car ran extremely well for about a year until a few weeks ago where the car seemed to stop revving past about 3.5k rpm. The car runs rich but it still idles fine and drives fine until the turbo starts to kick in, then the car hits 11.1 afr immediately and hits a wall around 3500 and starts sputtering and popping.

I brought the car to BrenTuning after trying to figure it out myself and they couldn't find what was causing the issue. They found no boost leaks, the MAF sensor is fine, and I replaced the o2 sensor to no avail. Does not occur in neutral, car will revs freely albeit a bit rich.

The symptoms are extremely similar to those described in this post from a while ago, but I never changed the injectors to anything else.
https://forums.nasioc.com/forums/sho....php?t=1083133

Thank you in advance for the help.
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Old 08-10-2022, 09:38 PM   #2
D-Rodman
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How new are the coil packs?


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Old 08-10-2022, 09:52 PM   #3
Alaaddin
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Quote:
Originally Posted by D-Rodman View Post
How new are the coil packs?


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One of them was replaced in October, and the rest of them seem fine.
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Old 08-11-2022, 05:41 PM   #4
Alaaddin
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Car has 2 CELs; p0172 and p0230 from the fuel pump
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Old 08-11-2022, 10:28 PM   #5
D-Rodman
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OBP BLACK

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Quote:
Originally Posted by Alaaddin View Post
One of them was replaced in October, and the rest of them seem fine.


Seem fine, did you test them ?


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Old 08-11-2022, 11:12 PM   #6
Alaaddin
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Quote:
Originally Posted by D-Rodman View Post
Seem fine, did you test them ?


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No, how can I do that?
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Old 08-12-2022, 12:39 AM   #7
D-Rodman
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OBP BLACK

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Search.


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Old 08-12-2022, 10:54 AM   #8
cboggess
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Quote:
Originally Posted by Alaaddin View Post
I have a 2004 STI with an EJ20x swap that I did not do myself.

The car has a Blouch TD05H-16gxt turbo, TGV deletes, catless up-pipe and downpipe, fuel pump hardwire, Tomei uel headers, front mount intercooler, hks bov, and an old protune on a v2 accessport.

The car ran extremely well for about a year until a few weeks ago where the car seemed to stop revving past about 3.5k rpm. The car runs rich but it still idles fine and drives fine until the turbo starts to kick in, then the car hits 11.1 afr immediately and hits a wall around 3500 and starts sputtering and popping.

I brought the car to BrenTuning after trying to figure it out myself and they couldn't find what was causing the issue. They found no boost leaks, the MAF sensor is fine, and I replaced the o2 sensor to no avail. Does not occur in neutral, car will revs freely albeit a bit rich.

The symptoms are extremely similar to those described in this post from a while ago, but I never changed the injectors to anything else.
https://forums.nasioc.com/forums/sho....php?t=1083133

Thank you in advance for the help.
I have seen this before, but only once. It was when our crank broke at the track. It had just enough "grip" between the broken parts that all seemed good until we put real load on it. At that point in time it would throw off the crank signal just enough that it would cut revs at 4500.

Start the car and take a look at the crank pulley. See if it's wobbling. If it is the pull the pulley off and see if the snout of the crank looks a little off center. If it is pull the timing and see if the crank will then wobble a bit by hand.

I really hope this is not the case for you.
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Old 08-12-2022, 02:36 PM   #9
Alaaddin
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Quote:
Originally Posted by cboggess View Post
I have seen this before, but only once. It was when our crank broke at the track. It had just enough "grip" between the broken parts that all seemed good until we put real load on it. At that point in time it would throw off the crank signal just enough that it would cut revs at 4500.

Start the car and take a look at the crank pulley. See if it's wobbling. If it is the pull the pulley off and see if the snout of the crank looks a little off center. If it is pull the timing and see if the crank will then wobble a bit by hand.

I really hope this is not the case for you.
I appreciate the suggestion, I'll be sure to check this out. But wouldn't this result in a misfire/timing code?
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Old 08-12-2022, 02:38 PM   #10
Alaaddin
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Does anyone know if a failing fuel pressure regulator would cause this?
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Old 08-13-2022, 11:36 AM   #11
D-Rodman
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OBP BLACK

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I know from experience weak spark from old coil packs will do that.


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Old 08-14-2022, 10:27 AM   #12
Alaaddin
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Quote:
Originally Posted by D-Rodman View Post
I know from experience weak spark from old coil packs will do that.


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I checked out my coil packs, I'm not able to properly test them without a tester, however, I did notice that the one that was replaced was numbered fk0334, while the rest were fk0186. This never gave me any issues, but if I were to go and replace the rest of them would it be best to use fk0334 or fk0186 coils?
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Old 08-14-2022, 12:56 PM   #13
motorbykemike
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coils should match

you should use the coils for your ecu

i have set of 04 sti coils with about 35k on them

pm me if interested

and maybe new plugs
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Old 08-14-2022, 01:29 PM   #14
Alaaddin
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Quote:
Originally Posted by motorbykemike View Post
coils should match

you should use the coils for your ecu

i have set of 04 sti coils with about 35k on them

pm me if interested

and maybe new plugs
pm sent
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Old 08-20-2022, 06:40 PM   #15
Alaaddin
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The coil packs did not change anything. Neither did a fuel pressure regulator.
Does anyone have any ideas?
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Old 08-21-2022, 08:24 PM   #16
D-Rodman
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Location: Long Island N.Y.
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02 Bugeye JDM STi
OBP BLACK

Default Car won't rev past 3.5k rpm

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Old 09-26-2022, 01:19 PM   #17
Alaaddin
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Problem solved!
It ended up being faulty wiring between the ecu and the maf sensor. After messing with it while doing some more in depth diagnosis the connection was improved and the problem resolved itself
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Old 09-26-2022, 03:02 PM   #18
benflynn
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Also…2020 black coils are the same as the 04, same dwell map. So grab a set of low mile take offs when they come avail.

Also seen another cause to this, stripped tab on crank timing pulley, was non interference so took a min to figure out, would not start, then catch and run, then go out of time. As an experience
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