I have Subaru Impreza 2.5i (2.5 NA). My car's engine sputters a bit when turning it off. Specifically it seems like the cars engine keeps turning for a little longer right after I remove the keys.

  • There don't seem to be any issues starting the car or driving it around.

  • There are no CELs

  • The only thing I can think of that's a little strange in the car's recent history is that I put in premium high octane fuel (the gas station was out of regular). I can't definitively connect the two incidents though. In between doing that and now, I also had to boost the car once since it was really cold. I don't know if the ECU reset with a premium fuel type would do anything... again, can't really connect the two. Its been long enough though that I think everything should be calibrated anyway.

  • The engine has < 40,000 km on it and the car is completely stock.

What are some reasons the engine could be sputtering? What could I try to diagnose the problem?

  • possible duplicate of Car diesels after shutoff
    – jscs
    Mar 7, 2015 at 9:15
  • Is there nothing I can do to try and diagnose the problem a little more on my own? What are some steps a mechanic might take if I took the car to a garage?
    – Pris
    Mar 7, 2015 at 14:10
  • Come over to the Chat. Mar 7, 2015 at 14:20

1 Answer 1


Its called in the UK "running on". Though I am not a Suburu expert, this is usually caused by a weak mixture,inlet air leaks, wrong grade spark plugs,wrong grade fuel,over advanced ignition timing, glowing carbon hot spots in the combustion chamber, leaking fuel injector, overheating engine, or on some engines a electric inlet suction break valve failing. Take the vehicle out for good long high speed drive and see if it helps, after that its electronic diagnostic checks on the system.

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