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This is a Subaru Forester 2003.

The car start losing power after a few minutes on the road. And suddenly lost all power and is almost impossible to drive.

Already changed:

  • fuel pump
  • spark plugs
  • ignition coil
  • O2 sensor
  • fuel filter

The car had no check engine codes. The catalytic converter is new, less than 3 years old.

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    Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Sep 19 '18 at 2:06
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    When you say there's no check engine codes does that mean that there's no check engine light on the dash, or that you've read the OBD codes using a reader? – GdD Sep 19 '18 at 7:24
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    Completely random guess, but did you check the earth straps. There should be a braided cable on each head, connecting the engine to the body. If one or both are missing, weird things can happen. They're often overlooked, and broken/torn off if the engine is removed without them being disconnected. – PeteCon Sep 19 '18 at 14:05
  • Has no Check engine codes at this moment, a while ago had the p0447 code which was a broken cable and the p0420 that says Catalyst System Efficiency Below Threshold) bank1. And the O2 code but I already replace the sensor already. Right now doesn't show any codes – Joel Yeti_974 Sep 19 '18 at 14:20
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    Do you have any way to test fuel pressure ? – Pierre P. Sep 19 '18 at 15:26
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Catalytic converters can go bad pretty quickly when engines are out of tune. p0420 is possibly that.

The definitive test is a pressure gauge where the O2 sensor is.

If the compression on the motor is good (compression test) you need to look elsewhere. If compression is low on all cylinders - timing belt jumped a tooth.

Vacuum gauge will also give you an idea. If, at idle, the vacuum slowly goes to zero, you are no longer 'pumping air' and also points to a clog.

I had one motor loose power when 3 rocker arms jumped off (Chrsler 4.7, overhead cam) Compression check was weird, leak down test was also weird. I suspect owner didn't change the oil often enough and hydraulic adjusters (like lifters) were all coked up/clogged. Reved it too much when cold.... No noise from engine, no check engine line, just way down on power.

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