2009 impreza non turbo 125k, recent head gasket installed at dealer. About a month or so later I started to notice a slight gas smell in the cabin after filling up. thought maybe I stepped in gas at the station, ran through the full tank and still smelled it. Seen a little gas at the top of pump. Replaced the seal and it was still leaking.. drove to work mon, tues, then wed it was running rough for about the first 1/2 mile then was fine the next 20miles. parked it for a few days then pulled into garage to replace the fuel pump with an aftermarket and it was running rough when i pulled it in... I replaced the fuel pump. Started it up and it was still rough when pulling out of driveway. Drives fine at low RPM and lower speeds until you get on the gas, then it sputters and shakes until i let off the gas or baby the petal. Check engine light, traction control, and cruise blinking. Checked the code and it said P0304 and P0304pd (pending display). Plugs and timing were replaced around 100k. any thoughts?

 

Fuel filter?

Sounds like a fuel filter. Had a civic the same thing, changed everything around it, finally we pulled the filter and that poor thing was so trash :(. 

IIRC should be under the hood on the driver side near the brake booster on tjose imprezas

 

Ignition. Loose plug wire, bad wire, bad plug, corrosion, etc. 

2009 fuel filter is in the tank with the pump assembly. Rarely a problem. Never seen it in fact. 

GD

Edited June 18, 20196 yr by GeneralDisorder

fuel pump is brand new.  I believe the filter is in the pump and this was happening right before and also after the fuel pump install.  Will  check the wires/plugs first.