Smooth Idle, Dies Beyond 20 Percent Throttle Opening

[That_04_STi]

Evening Everybody,



I have an issue I've been chasing for some time now and it seems I am having trouble getting this figured out.





ADMIN DATA

- 2004 STI

- Stock EJ257

- Arashi 20G 3in 10cm Internally Gated 15psi

- MAC 3-port EBCS

- Catless downpipe

- 3in Inlet

- Stock Yellow Side Feed Injectors 550cc

- 340lph Fuel Pump

- Short Ram CAI

- Cat-Back Borla Silencer Exhaust

- FMIC

- Stock BPV

- NGK One Step Colder plugs



ISSUE

- Currently in the middle of E-tuning my car through OpenSource, RomRaider/ECUFlash.



DURING IDLE:

Car wants to take time to start, then wants to idle just fine. High idle during warm up process, then 900rpm idle when warm. Once given throttle, anything beyond 20% throttle as I'm watching the Logger, the car wants to almost choke itself. If you have anything less than 20% throttle it wil slowly climb in RPMs. But, once it reaches 2500-3000RPMs the car wants to stumble and fall on its face.



UNDER LOAD:

While driving the car, it will drive just fine for about 5-10 minutes, it is not consistent, and then it will not go beyond 2500-3000 RPMs. Same issue with the throttle as it will not let me reach beyond 20% throttle opening without having it fall on its face. It will then drop very low in idle and work its way back up to about 1200RPMs and then smooth out and drop back down to 900RPMs. This entire time, when in vacuum, the boost gauge reads -20.



POSSIBLE SOLUTIONS



- The tuner has since mentioned checking all of my grounds and then trying it again. I have checked them all, cleaned them, and tightened them down.



- I have cleaned and resealed the MAF sensor with a new O-Ring as this what brought up in other forums.



- I have gone through all of the FMIC piping and taken it apart and resealed it as a vacuum/boost leak might be evident.





I can supply data logs if anyone is interested in looking over them.



Thank you,

Chris

* Registered users of the site do not see these ads.

[dryvby]

Mmmm, lazy injector(s)? Are they new or have they been on a flow bench.

[That_04_STi]

Originally Posted by dryvby

Mmmm, lazy injector(s)? Are they new or have they been on a flow bench.

I haven’t had them cleaned or flow tested since I’ve owned them, but for sure could be a possibility. Hopefully I could get them on a cleaning and testing bench within the next week and see if that’s it.

[That_04_STi]

Can someone help me figure this out. It’s still an issue.

[kopele]

Can you post a log? Does it still happen if you reset the ECU?

[That_04_STi]

I’ll get one up in about an hour. I just took one today. So, now whenever I shut off and restart the car or reset the ECU, the car will run fine for about 3-5 minutes then it will start doing the same thing again progressively getting worse with every time pushing down the throttle. Maybe something is learning and it’s messing everything up.

[A.S.N.F.]

I would also be suspicious of fuel. Like a weak fuel pump, clogged fuel filter ect.

[That_04_STi]

Evening everyone,

I have since put more fuel in the car, thinking maybe the gauge is just off severely, and then I went ahead and started the car. I let it warm up and the issue seemed to go away for about five minutes. I drove the car for about 3-5 minutes and then it all happened again, but this time it isn't throttle dependent. At first, it starts acting up around 5000 rpms, then as time goes on it'll continue to act up but progressively do it as you get lower in the RPM range. So, it'll do it at 5000, but then 5 seconds later it'll do it at 4000, and then so on and so forth untilm it gets down to 2500, where it stays. At this point the car is not driveable at all, it lugs and hips and hops and doesn't know what to do with itself. the sound is almost as if the car has a 2 step of some sort on it whenever it hits those target RPM ranges, but then will want to die just after.

Thanks again everyone for the help.

[A.S.N.F.]

If your exhaust does not sound blocked (like a catalytic converter coming apart) I would pull the fuel pump and look for leaks where it is mounted and check the sock. If you have a fuel pressure sensor you could check this easily, however if you can see the duty cycle and if those step up line mine (where it will run 33%, 66% or 100%) you could also check that, as it will step up as it is loosing fuel. Cause it seems like something is getting blocked. If you have a MAF you could make sure its reading something too in closed loop but I don't think its that.

[That_04_STi]

You guys are awesome! Thank you every for the help! I figured out the issue. Fuel pump was bad after I had it tested for pressure. It would work for about 3-5 minutes then would taper off slowly.