2.5 Subaru stutter at 5k

HP.Habits

HP.Habits

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I have a 2.5 Subaru I am trying to trouble shoot why it wont get past 5k rpm. Engine starts to stutter like its not getting enough fuel. only pushing around 10# boost...

It has new ignition coil pack, ign. wires, mapping sensor, new fuel lines, new fuel pump, new fuel filter... couldnt get past 5k.. I got new spark plugs, gapped to .025 and that helped it get to about 5300 rpm, motor seemed way more crisp leading up to it too (I was convinced rolling onto the throttle it was fixed with how much better it was running), but still not it..... any other suggestions?

 
no, These are all the items that have been replaced chasing down the issue.

Oh, Also just cleaned the Injectors. 

 
something to ponder on my voyage of gremlins.....crank sensor (center of the block by exhaust), timing belt/cam sensor (right side rear of motor), and the sneaky one MAF sensor on the intake is dirty or bad. Another consideration I almost did was the CPU and tuning/re-wire. However, hard and kinda expensive $3000+ to find a tuner that has time and ability to re-wire/merge into a new CPU but they are out there....let me know. can't wait to hear about the new chasis you are going to have done. that 2 seater is the bees knees. 

 
Following.  Mine does the same thing.  I'll be doing a new ECU and wiring soon, followed by a tune.  Hope to flush it out then.

 
Mine was doing the same thing a while ago. I put new plugs in gapped @ .020 and fixed it.  I put fresh plugs in a couple times a season

 
I had similar issue and it turned out to be a fuel pump. Made good pressure at idle but would fall on its face under a load. 

 
Pennywise said:
I had similar issue and it turned out to be a fuel pump. Made good pressure at idle but would fall on its face under a load. 
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I have had that issue too. I forgot about that one. Pump chewed itself apart inside. We found the problem on the dyno. Pressure was good till you put load on the motor

 
Check fuel delivery out of the tank. on my first gen 3 after about a season all of the sudden it ran like chit was missing at high rpm. ended up having some alum shavings right out of the tank .

 
Just reading through this.  Kind of a crappy problem with no solid lead or fix.  Some say filters, some plugs, some pump.

Has anyone tried zip tying a wad of $100 bills to it and see if that fixes it?

 
Does it rev clean to the limiter in neutral, just under boost, or any time you try to clear 5300rpm?

 
Since most of this was done before the injectors, I figured for sure it would be injectors. On my Orange Funco, I had to clean injectors at least once a season, otherwise it acted the same.... 

 
Rockwood said:
Does it rev clean to the limiter in neutral, just under boost, or any time you try to clear 5300rpm?
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I never really like to rev to the limiter in Neutral. Ill rev it when I get home to day and see. Im starting to think maybe the pump isnt keeping up... 

 
HP.Habits said:
I never really like to rev to the limiter in Neutral. Ill rev it when I get home to day and see. Im starting to think maybe the pump isnt keeping up... 
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Rules a lot of things out.  No need to bang the limiter, but if it has no trouble clearing 5300rpm in neutral, it's a bulk supply or spark issue.  If it doesn't, it's probably ECU or signal related (like CPS).  

Is the fuel pressure regulator vacuum/boost referenced (have a line from the intake manifold to it)?

 
If your FPR has a gauge (it should), and you can put a gopro (or the like) on it, take it for a rip while recording fuel pressure.

 
I warmed up the car and revved it up when I got home, unfortunately it did not make it past 5300... I am in contact with a couple different tuners up here in UT to see if we can get it plugged in and maybe see some helpful messages, or just retune...

 
Even though its not resolved, I just want to give a quick thanks to you all for your suggestions. learned a few things and definitely appreciate the help! 

 
HP.Habits said:
I warmed up the car and revved it up when I got home, unfortunately it did not make it past 5300... I am in contact with a couple different tuners up here in UT to see if we can get it plugged in and maybe see some helpful messages, or just retune...
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Check the cam or crank position sensor? I remember there being something about them getting finicky on Subarus

 
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