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Old 07-28-2013, 03:42 PM   #1
silver_echo
Scooby Specialist
 
Member#: 241296
Join Date: Mar 2010
Chapter/Region: NWIC
Location: Spokane, WA
Vehicle:
2002 wrx
aspen white

Default Help with a 2.5 na.

So, vehicle is a 96 legacy wagon, 2.5 quad cam, auto.

Symptom is large hesitation/miss with throttle input at the level to hold speed in a parking lot(~10-15mph). Also, engine is sluggish below 3k rpm.

Codes thrown: map sensor range/performance, catalyst efficiency below threshold, o2 sensor circuit.

Checked cats at local muffler shop, cats are good.

Swapped out map sensor with another one from local wrecking yard(watched live data stream after swapping, functions normal).

History of vehicle: unknown before about 5k ago(purchased with ~220k). Since then, head gaskets replaced with full timing kit, plugs, wires, air filter, pcv valve, tranny work, burned valves replaced, replaced front brakes after caliper slide seized, new fuel filter.

Only other issue known at this time is a minor oil leak from oil cooler.

Any help/knowledge would be appreciated.
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Old 07-28-2013, 05:15 PM   #2
silver_echo
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Member#: 241296
Join Date: Mar 2010
Chapter/Region: NWIC
Location: Spokane, WA
Vehicle:
2002 wrx
aspen white

Default

Symptom is not present during cold start warm up.
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Old 08-01-2013, 03:03 PM   #3
Mr_Furious
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Member#: 298713
Join Date: Oct 2011
Location: Vancouver, Canada
Vehicle:
1997 Impreza, Wagon
Blue

Default

did you change the o2 sensor?
if it's shot when you are in closed loop (low throttle) it will send really erratic signals to the ecu and it will run rich lean rich lean and be gutless.
I had a similar problem and only really saw it after I installed a wideband and guage
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Old 08-02-2013, 03:03 AM   #4
silver_echo
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Member#: 241296
Join Date: Mar 2010
Chapter/Region: NWIC
Location: Spokane, WA
Vehicle:
2002 wrx
aspen white

Default

Quote:
Originally Posted by Mr_Furious View Post
did you change the o2 sensor?
if it's shot when you are in closed loop (low throttle) it will send really erratic signals to the ecu and it will run rich lean rich lean and be gutless.
I had a similar problem and only really saw it after I installed a wideband and guage
I will try it. Found main engine ground wire grounded out to egr tube. Issue got much better. Still just barely there, but a much smaller window of the throttle, and not as bad anymore. Think maybe sensor was damaged by fluctuating power levels.
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Old 08-02-2013, 05:38 PM   #5
yarrgh
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Member#: 80465
Join Date: Jan 2005
Chapter/Region: RMIC
Location: Aurora, CO
Vehicle:
2001 2.5RS
Black Diamond Pearl

Default

try cleaning ALL of the grounds to the engine and see if that also helps.
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