Subaru WRX Forum banner
Cancel
Create thread New Garage Forums

P0171, bad idle, low power, stuttering

1 reading
Jump to Latest
36K views 16 replies 9 participants last post by  SD_GR  
B
#1 ·
Hi,
My WRX has had some issues lately. It use to show a misfire cylinder 3 code so I changed the spark plugs and seafoamed the intake. Now there is a P0171 - System too lean (Bank 1). It's idling really low (750 rpms), stalling when I push the clutch in, and it feels really low on power. The boost gauge says I'm at the correct psi for stage 2, and it's holding pretty well, but the car feels like it has the same power as it did when it was stock. When I accelerate with about 30% throttle, the car will be fine until about 3000-3400 RPM where it will jerk a few times and lose 50% power, then repeats this from 4000-4250 RPM. I changed my oil yesterday and there were specks of metal. It looked like flake in metallic paint so I'm sending the oil out to be analyzed. I have cleaned the IACV, the MAF, and seafoamed the fuel but nothing has made a difference. Is my engine in bad shape? Could this be a problem with my fuel system? I just need someone to point me in the right direction.
 
B
#4 ·
I've never changed the fuel filter in the ~40,000 miles that I've owned the car. It has 80,000 now. Could bad injectors be a suspect, too?

Donkey said:
P0171
Fuel trim malfunction (A/F too lean)

Your car is supposed to idle at 750rpm at full warm up........
Sounds like you maybe borked the O2 sensor.How exactly did you do the Seafoam treatment for the intake?Please don't tell me you used the brake booster line.
Click to expand...
I used the vaccuum hose off the BPV. Maybe all the carbon crud fubar'd the O2 sensor? I'm guessing it would be the front sensor (A/F).
 
#3 ·
P0171
Fuel trim malfunction (A/F too lean)

Your car is supposed to idle at 750rpm at full warm up........
Sounds like you maybe borked the O2 sensor.How exactly did you do the Seafoam treatment for the intake?Please don't tell me you used the brake booster line.
 
#9 ·
I had this problem a couple nights ago. When a vacuum line pops off, it causes the idle to run lean. That's what throws the p0171 code. I resecured the vac hose with a hose clamp, and sure as sh1t, the thing runs like a champ again.
 
#10 ·
do you have an accessport? Because I can help you diagnose the problem
 
#12 ·
The return line to the manifold from the fuel evap solenoid.
 
#17 ·
Subaru WRX Forum
posts
3.2M
members
157K
Since
2001
We invite you to join our Subaru Impreza WRX and STi community to discuss engine mods, builds, detailing, and more.
Full Forum Listing
Explore Our Forums
Engine Modifications Everyday Impreza Talk General Maintenance, Troubleshooting & Accidents. Exterior & Appearance Comparison: WRX vs World