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I'm fixing up an old 2002 Subaru Impreza (2.5L), and the only problem left is that on heavy acceleration, such as up hills, the vehicle chugs and stutters a lot, even comes close to the engine dying. Once the accelerator eases off, or after the car is started up again if it dies, things are generally fine again until heavy acceleration occurs once more.

Could this be the fuel injectors? I have isolated and confirmed that it is none of the following:

  • Fuel pump
  • Fuel filter
  • Plugs/wires
  • Ignition coil
  • O2 sensor

Besides the fuel injectors, the only other thing I can think of is the MAF sensor, but I don't have the means to test this just yet. I'll do the injectors first (unless I'm way off base) and go from there. My next question is -- where are the injectors on this engine?! I can't even find the fuel rail:

top-down view of engine

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    Welcome to Motor Vehicle Maintenance & Repair! How have you confirmed the fuel pump? Unless you are measuring the fuel pressure at WOT up hill (or whatever is the problem area), you really don't know for sure. Also, check the TPS reading at the point at which you are seeing the issue. Commented Sep 8, 2023 at 19:37
  • Thanks! The reason I'm confident it's not the fuel pump is because I replaced the fuel pump with a new one (along with a new fuel tank, since the old one was punctured). The problem persisted after fuel pump replacement which makes me think that isn't the issue! Commented Sep 8, 2023 at 19:47
  • That is a fair reason to think it's not the fuel pump, but don't discount it completely. Commented Sep 8, 2023 at 19:59
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    Error code(s) stored in memory turns on the check engine. No cel = no errors. The boxer engine splits the main fuel line into two branches, there may be a fuel test valve somewhere on the fuel line. If you can determine fuel line routing, they should lead to injectors. Presuming fuel pump replacement is fine, is there an external fuel filter? Presuming fuel pressure is fine, leaves the possibility of cvt issues and sometimes difficult to diagnose by diyers. I'm still looking under the hood of my new Crosstrek Sport 2.5L to learn where everything is. CVT faults may not have error codes. Catcon?
    – F Dryer
    Commented Sep 8, 2023 at 22:09
  • Thank you! I did find the injectors by tracing the fuel line from the fuel filter. First step complete... Commented Sep 9, 2023 at 0:55

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