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GB270 mis-fire

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Hi, I'm new to the site but was wondering if anyone could help with a problem I have with my GB270. Sorry for a bit of a saga, but hopefully it provides most details needed for help....

Impreza GB270 2007, secondary air injection system turned off in ECU.

Recently ran fuel lower than normal then had to put in small amount of 95 RON. Ran for about 70 miles very gently then topped up with Shell V-Power. After another tank of V-Power, got some hesitation when cold which quickly turned to
mis-fire all the time. Have only had a fault code once (mis-fire cylinder 4) which was cleared and has not re-appeared after driving 7 miles whilst missing. (not using now, thankfully have spare 2000 Turbo  )

Have tried new coil pack and plug in cylinder 4, no difference. Ran whilst coil pack off cylinder 4 and no noticeable difference, suggesting the problem is with cylinder 4.

Does anyone have any ideas what could be checked next or advise best place to take car to in the Norfolk area.

Any help would be much appreciated.



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Hi mate welcome to S.O.C 


Could be a few things I'm guessing you have checked them all but will re list just incase or if it helps anyone else browsing :D


  1.  Blocked injectors/dirty fuel filter
  2. Wrong/Worn or incorrectly gapped spark plugs
  3. Possible Maf giving a wrong reading to make one misfire. But normally it cuts the engine out at low speeds.
  4. Vacuum leaks. Check all the pipes for splits or loose connections  
  5. Battery ground cable and ones that run to the intake manifold. Make sure they're clean and coilpack bolt holes.
  6. Bad/loose coil pack or coil pack connector
  7. PCV valve. might need replacing 
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  • 3 weeks later...

Finally got the car fixed. It went to a local diagnostic expert / tuner Clive Atthowe (www.enginetuning.net) who eventually traced the fault to a dodgy connection within a large connector block between ECU and the engine. The injector on cylinder 4 was not grounding properly and hence closing gradually whilst it should be open, causing the misfire. Rather than split the connector and potentially cause more problems, a wire was soldered across the block for this cable only. The car is running sweet as a nut again, phew. Thanks again for all the advise given earlier.

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