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01-28-2006, 01:02 AM | #1 |
Scooby Specialist
Member#: 86854
Join Date: May 2005
Chapter/Region:
Tri-State
Location: Rockland, NY
Vehicle:2004 fx35 02 Z06 Beryllium, Millenium Yell |
Help me figure out why my car is bucking/bogging at certain RPMS!
as the title says... When the car is cold (first start up) it idles around 1400 rpms, and if i blip the throttle slightly it sounds the my car has a heavy cam, it kinda sounds like a vacuum leak. When the car is at NOT and I blip the throttle slightly, the rpms drop from normal 750rpm to about 620ish and it feels like its about to stall, but it doesnt, it just jumps back up to normal rpm range(I can tell by the AVC-R)
Now, when im in 2nd-4th gear, the car sometimes bucks and boggs at like 50% throttle from about 2500rpm to about 4K... it only does it sometimes though. When im decellerating in 2nd-4th and the rpms are between 2500-4K, and i lightly press the throttle, the car starts bucking/bogging again and sort of jumps very slightly... My mods are: VF39 Pinks header UTEC AVC-R stock airbox sti tmic 3 inch TBE Forge BOV Greddy Catch Can Like I said, it sounds like a vacuum leak but Ive checked and re-checked all of the connections and have not seen anything wrong. The BOV is not leaking and all hoses are fine. Anyone have any idea of what it could be? Thanks for the advice neel
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01-28-2006, 03:30 PM | #2 |
Scooby Newbie
Member#: 35475
Join Date: Apr 2003
Chapter/Region:
SCIC
Location: OC, CA
Vehicle:2013 STi Black |
Not too sure about the bucking while driving but sounds like the idle problems I have been hearing about alot lately. There is a sticky on the service and maintenance forum about cleaning and reattaching the idle air control valve. Maybe that can help.....
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01-29-2006, 12:40 AM | #3 |
Scooby Specialist
Member#: 86854
Join Date: May 2005
Chapter/Region:
Tri-State
Location: Rockland, NY
Vehicle:2004 fx35 02 Z06 Beryllium, Millenium Yell |
anyone else?
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01-29-2006, 12:57 AM | #4 |
Scooby Specialist
Member#: 79394
Join Date: Jan 2005
Location: reston
Vehicle:02 gda wrb |
how are your injectors working?
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01-29-2006, 01:03 AM | #5 | |
Scooby Specialist
Member#: 86854
Join Date: May 2005
Chapter/Region:
Tri-State
Location: Rockland, NY
Vehicle:2004 fx35 02 Z06 Beryllium, Millenium Yell |
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01-29-2006, 10:08 AM | #6 |
Scooby Newbie
Member#: 106084
Join Date: Jan 2006
Chapter/Region:
South East
Location: New Bern, North Carolina
Vehicle:2003 WRX Wagon Black |
How long has it been doing this? and was there a mod that you did prior to this starting...I ask because I had a similar situation when I first installed the AVCR on my 03 WRX. I also had the problem after switching from AVCR to TXS manual boost controller...I switched to manual because the AVCR and stock ECU didn't get along. The TXS was a waist gate issue that was easy to fix. But I see you have UTEC so that may not be the problem. Was just curious if your AVCR was a new mod.
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01-29-2006, 02:11 PM | #7 |
Scooby Newbie
Member#: 105921
Join Date: Jan 2006
Chapter/Region:
MWSOC
Location: Dayton, ohio
Vehicle:2007 Impreza WRX STi Obsidian Black Pearl |
Mis-fire
Now im use to tuning other cars and this is my first wrx but aside fromt he vacuum leak have you considered a bad plugwire or plug or even a mis-fire code in the ecu. Have it checked at like autozone and see what they say. Just a suggestion. Good luck.
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01-29-2006, 10:56 PM | #8 | |
Scooby Specialist
Member#: 86854
Join Date: May 2005
Chapter/Region:
Tri-State
Location: Rockland, NY
Vehicle:2004 fx35 02 Z06 Beryllium, Millenium Yell |
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01-30-2006, 04:10 AM | #9 |
Scooby Guru
Member#: 48219
Join Date: Nov 2003
Chapter/Region:
MAIC
Location: Pittsburgh, PA
Vehicle:. Always drive the race line . |
sounds like you need slightly more tip-in enrichment. if bet if you were to log the AFR you'd notice the car is running lean for a second while it's stumbling.
try wrxhackers.com. they might be able to help you with that since there's a big UTEC community there. i actually got fed up of having to deal with the UTEC. i've got a different EM now. |
01-30-2006, 02:29 PM | #10 | |
Scooby Specialist
Member#: 86854
Join Date: May 2005
Chapter/Region:
Tri-State
Location: Rockland, NY
Vehicle:2004 fx35 02 Z06 Beryllium, Millenium Yell |
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01-30-2006, 04:45 PM | #11 |
Scooby Guru
Member#: 48219
Join Date: Nov 2003
Chapter/Region:
MAIC
Location: Pittsburgh, PA
Vehicle:. Always drive the race line . |
basically when you open the throttle quickly there is a sudden rush of air that comes in which isn't measured as correctly as it should. so there is more air going in that fuel. to combat that, every single EM including the stock ECU will have a table for 'tip-in enrichment'
so if the change in throttle is let's say 5% it'll add X amount of fuel on TOP of what is already programmed in. if the change in throttle is 10% then it'll add Y amount of fuel on TOP of what is already programmed in. the tables go up to a certain percentage of change in throttle and have corresponding values for fuel enrichment. I don't think the utec has anything like that. but there is a way for you to reflash your own stock ECU yourself with a laptop and go in there and change the tip-in enrichment yourself. |
01-30-2006, 08:29 PM | #12 |
Scooby Specialist
Member#: 81123
Join Date: Feb 2005
Location: Louisville, KY
Vehicle:2002 2.5 WRX BY RIP 02' 2.5WRX PSM |
I think it has to do with the UTEC. I had a bunch of problems with hesitation and bucking due to 50% or so throttle. Had it tuned professionally, twice.
Has it been professionally tuned beyond an off-the-shelf-map? Sometimes if your throttle position is right at the CL to OL transistion (say 25%), and you keep it there - you can get a more pronounced roughness or hesitation. Its almost like - you need to be under your TPS point or way above it, Not right at it (which seems to be the position of daily stoplight to stoplight driving.) That was my experience with UTEC. I have since went with different EMS with better luck. Another thought: Is your BOV recirculating or Atmospheric? Could be an issue if its atmospheric. Good Luck. |
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