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Old 05-09-2012, 12:56 AM   #1
cobra280z
Scooby Newbie
 
Member#: 274036
Join Date: Feb 2011
Default 2003 hesitation/lean code

Hello,
I've been wrestling with this issue for some time, with no good results. The car is 2003 wrx wagon, about 95000 miles. For the last couple on months I've been having issues with hesitation under load. I get good acceleration in first and second at WOT, with good boost readings. However, in third, I get hesitation under partial or WOT. The boost readings are good (~13 psi) and do not fluctuate. However, the engine just has little pull and bucks/hesitates slightly. The bucking/hesitating is much more pronounced at partial throttle in 2nd and 3rd gear.
In addition to this, I get a lean code occasionally (4 times in 2 months). The code seems to happen come up particularly when driving up an extended hill, at partial throttle, around 2500-4000 rpms for longer periods of time (this would also be the range where I feel the hesitation the most. Long drives on the highway at low load don't trigger a code, nor do harder pulls at WOT.
Here's what I have done so far:
replaced fuel filter
replaced BCS
replaced spark plugs (old plugs all looked the same, just old)
run BG 44k through fuel
performed compression test on intake, no leaks
run fuel pressure test (2-3 psi high across the board)
cleaned MAF several times
replaced PCV
checked coils visually (peeled back rubber grommet)

So far, the problem seems to have gotten slightly better after running the BG 44k through the fuel. The car idles perfectly and feels great until I try to accelerate aggressively or climb a steady grade. My thoughts currently are that the car isn't getting enough fuel (i"m thinking clogged injector(s)), though I'm certainly no expert.
Sorry for the long thread; I'm pretty frustrated with this, and I appreciate all responses.
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Old 06-03-2012, 12:08 AM   #2
07imprezRS
Scooby Specialist
 
Member#: 164302
Join Date: Nov 2007
Chapter/Region: SWIC
Location: Arizona
Vehicle:
11 STi DGM, 07 WRX
WRB, 02 WRX WRB

Default

Not sure if you've fixed your lean code or hesitation yet but mine was hesitating yesterday around 4.5k rpm. Inspected Mass air flow and cleaned it and noticed my K&N drop in filter was pretty dirty... Thoroughly cleaned it and reapplied the K&N filter oil and she's running sooo much better. Sounds simple but try looking at your air filter if you haven't done so already (didn't notice it on your list).
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Old 06-03-2012, 12:11 AM   #3
07imprezRS
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Member#: 164302
Join Date: Nov 2007
Chapter/Region: SWIC
Location: Arizona
Vehicle:
11 STi DGM, 07 WRX
WRB, 02 WRX WRB

Default

Also if not filter then either your injectors as you mentioned need replacing or possible leak in turbo inlet? How was the pressure test done for intake?
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Old 06-03-2012, 12:45 AM   #4
cobra280z
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Default

I've cleaned the MAF extensively, and the filter is fairly new. I want to try switching the MAF out with a known good one to eliminate that; I also want to clean the fuel sock. I did the pressure test just behind the MAF with a homemade fitting and compressor; the system held air well for at least 20 seconds. I have noticed that a tab appears to be missing on the air box, which could allow some air in; however my thought is that it wouldn't matter since it is pre-MAF. Appreciate the replies.
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Old 06-03-2012, 04:50 AM   #5
07imprezRS
Scooby Specialist
 
Member#: 164302
Join Date: Nov 2007
Chapter/Region: SWIC
Location: Arizona
Vehicle:
11 STi DGM, 07 WRX
WRB, 02 WRX WRB

Default

Are you running the stock bpv or aftermarket bov of some type? Could leak air under higher lbs of boost on the aftermarket if the spring is not adjusted properly or has become weak over time. I would try replacing or using a good maf sensor to see if yours is bad also like you stated.
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Old 06-04-2012, 01:21 AM   #6
cobra280z
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Member#: 274036
Join Date: Feb 2011
Default

Running stock BPV. Leaking air would create a rich condition (i'm getting the lean code), yea? And lower than stock psi, I would think. Working on testing MAF; also going to get an OBD2 cable to hookup to my laptop, start monitoring the car while its running. I'd like to change the turbo inlet tube as well, as its gotten quite soft (doesn't appear to be leaking yet, tho)- this will have to wait awhile unfortunately. Thanks for the input.
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