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07-14-2013, 09:03 PM | #1 |
Scooby Newbie
Member#: 293509
Join Date: Sep 2011
Location: New Orleans, LA
Vehicle:2004 WRX STI Blue |
TERRIBLE hesitation/lean AFR at low rpms. Particularly from a stop.
Just finished having my motor built on my 2004 STI and met up with my tuner (who has always given me solid tunes) to give me a break in tune but no matter what he tries the car goes EXTREMELY lean and hesitates like f'ing crazy to get moving from a stop until about 2700 when it suddenly runs like a charm.
This happens about 75% of the time, otherwise it gets moving perfectly fine. The issue also occasionally affects other gears as well at low RPMs (though not as much and not near as bad) and the car also is hesitating and not lettting me rev past the low 2000s during neutral revs about 50% of the time. Car is idling at a rock solid 14.7 afr. What is going on??? Spark plugs? Injectors? Mods include FP Red, 1100DWs, and other supporting mods. Tuning is on Cobb AP.
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Last edited by jesseber; 07-14-2013 at 09:39 PM. |
07-15-2013, 06:01 AM | #2 |
Scooby Specialist
Member#: 283711
Join Date: May 2011
Chapter/Region:
NESIC
Location: Newport
Vehicle:2012 STI sedan Black with scratches |
Did you check your fuel pump/regulator/controller already?
Last edited by dstroy; 07-15-2013 at 06:08 AM. |
07-15-2013, 12:58 PM | #3 |
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AFRs are still target when WOT?
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07-15-2013, 01:14 PM | #4 |
Scooby Newbie
Member#: 293509
Join Date: Sep 2011
Location: New Orleans, LA
Vehicle:2004 WRX STI Blue |
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07-15-2013, 01:15 PM | #5 |
Scooby Newbie
Member#: 293509
Join Date: Sep 2011
Location: New Orleans, LA
Vehicle:2004 WRX STI Blue |
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07-15-2013, 02:11 PM | #6 |
Former Vendor
Member#: 282460
Join Date: May 2011
Chapter/Region:
MWSOC
Location: Villa Park, IL
Vehicle:2005 Evo-STI R.R.-WRB |
The nuetral revs, that's a bit odd.
The rest of it sounds like it can stem from bent or kinked fuel hoses or a faulty regulator or coinciding vacuum assembly. Have you checked static and dynamig fuel pressure? -Mark |
07-15-2013, 02:22 PM | #7 |
Scooby Newbie
Member#: 153056
Join Date: Jul 2007
Location: NOLA
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At idle the dynamic fuel pressure on the gauge is at 42psi.
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07-15-2013, 02:35 PM | #8 |
Scooby Newbie
Member#: 293509
Join Date: Sep 2011
Location: New Orleans, LA
Vehicle:2004 WRX STI Blue |
^^ (Tuner) ^^
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07-15-2013, 04:56 PM | #9 |
Scooby Specialist
Member#: 283711
Join Date: May 2011
Chapter/Region:
NESIC
Location: Newport
Vehicle:2012 STI sedan Black with scratches |
Have a friend watch your pressure to see what it does, if it drops at idle, signs point to bad or going bad relay/fuse/wiring/pump/fpc. Or maybe a partially clogged filter.
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07-15-2013, 05:52 PM | #10 |
Former Vendor
Member#: 282460
Join Date: May 2011
Chapter/Region:
MWSOC
Location: Villa Park, IL
Vehicle:2005 Evo-STI R.R.-WRB |
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07-15-2013, 10:00 PM | #11 |
Scooby Newbie
Member#: 293509
Join Date: Sep 2011
Location: New Orleans, LA
Vehicle:2004 WRX STI Blue |
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07-15-2013, 10:39 PM | #12 |
Scooby Specialist
Member#: 283711
Join Date: May 2011
Chapter/Region:
NESIC
Location: Newport
Vehicle:2012 STI sedan Black with scratches |
Yeah, it'll tell you to either continue troubleshooting the fuel system or look for something else. You'd be looking for a significant drop in pressure.
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07-17-2013, 03:03 PM | #13 |
Scooby Newbie
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Location: New Orleans, LA
Vehicle:2004 WRX STI Blue |
Gonna pull and replace the fuel pump today and then check the FP gauge under throttle/stumble.
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07-17-2013, 11:47 PM | #14 |
Scooby Newbie
Member#: 293509
Join Date: Sep 2011
Location: New Orleans, LA
Vehicle:2004 WRX STI Blue |
Replaced fuel pump. No difference. Still 42psi at idle, climbing to ~55psi under sputtering free rev.
Having played with it more, I have to say the hesitation is the worst whilst going into 1st. Almost impossible to get going when it stumbles. Update: Moved it out of the way of my driveway a few minutes later and it acted absolutely perfectly well behaved (for the two times I gave it pedal while semi-walking it). Gave it some free revs afterwards and after a few it started stumbling again. Also, just caught p0458 (Evap) but if I'm not mistaken that's because of my new Perrin fuel rails/lines, correct? Last edited by jesseber; 07-17-2013 at 11:54 PM. |
07-18-2013, 09:41 AM | #15 |
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Hey you did not mention that you also have intake camshaft position sensor DTC (p0021) that keeps popping out from time to time and also P0011. Having those DTCs coming on will also render the car from operating normally. I mentioned these to you from the day I got to the mechanic shop and connected to the AP unit to try to tune it.
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07-18-2013, 09:45 AM | #16 |
Scooby Specialist
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Hang on... You got an evap code? did you by chance NOT hook the evap purge line on the manifold back up? Because that would give you a pretty significant vacuum leak.
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07-18-2013, 09:50 AM | #17 |
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And if your AVCS solenoid/related wiring is failing it would cause problems similar to this.
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07-18-2013, 02:51 PM | #18 |
Former Vendor
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Join Date: May 2011
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Location: Villa Park, IL
Vehicle:2005 Evo-STI R.R.-WRB |
hmmmm, looks like there are other things going on here...
-Mark |
07-18-2013, 02:53 PM | #19 | |
Former Vendor
Member#: 282460
Join Date: May 2011
Chapter/Region:
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Location: Villa Park, IL
Vehicle:2005 Evo-STI R.R.-WRB |
Quote:
huh, odd that things get left out randomly. -Mark |
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07-18-2013, 04:02 PM | #20 |
Scooby Newbie
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Last edited by jesseber; 07-18-2013 at 04:21 PM. |
07-18-2013, 04:04 PM | #21 | |
Scooby Newbie
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Vehicle:2004 WRX STI Blue |
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07-18-2013, 05:00 PM | #22 |
Scooby Specialist
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Join Date: May 2011
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You need to do a leak test to rule out any vacuum leaks.
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07-18-2013, 05:13 PM | #23 |
Scooby Newbie
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Location: New Orleans, LA
Vehicle:2004 WRX STI Blue |
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07-18-2013, 05:26 PM | #24 |
Scooby Specialist
Member#: 283711
Join Date: May 2011
Chapter/Region:
NESIC
Location: Newport
Vehicle:2012 STI sedan Black with scratches |
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07-19-2013, 04:32 AM | #25 | |
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