On my Mitsubishi shogun sport van 2002 3.0L V6, There was a slight misfire on cylinder 5. We replaced spark plugs, all the HT leads (Ignition wires) and Ignition coils (all 3). That didn't solve our issue so we checked for compression and it was all normal and every cylinder was the same so then we replaced all the fuel injectors and it still hasn't solved the misfire. It use to pop up as an error code but doesn't anymore and doesn't show up with any engine lights. It seems to start backfiring longer the car has been running/Idling (backfires more as the engine gets hot) We are thinking the electrics deeper in the car? Please help.

  • You've replaced all the usual stuff. Is it possible there is a bad valve lifter? I'm not familiar with that engine but a pushrod engine can get a collapsed lifter and the valve may not open as much as it should. Less common with an overhead cam engine but the cam lobe could be damaged or the valve itself may be worn. Could also be piston rings. You might try a leakdown test.
    – jwh20
    Aug 5, 2021 at 18:59
  • Welcome to Motor Vehicle Maintenance & Repair! Have you checked your fuel pressure at the rail? Aug 5, 2021 at 21:09
  • When you use the term “backfiring”, do you literally mean that you are hearing explosions in the exhaust pipe?
    – HandyHowie
    Aug 6, 2021 at 14:02
  • By Backfiring I mean a pop that sounds like its from the exhaust pipe Aug 6, 2021 at 16:50

1 Answer 1


Try searching for Mitsubishi forums with owners, techs and mechanics familiar with your model. There's always someone with more knowledge, experience and skills in specific forums as a way to use the internet message boards of sharing free info instead of relying on dealer or repair shops.

Misfiring may be more complicated if it wasn't fixed with plugs, wires, ignition coils and compression checks (for mechanical health). The EFI system may be the next steps in diagnosing this misfire issue. Fuel pressure was mentioned to check. Fuel filter may need replacing at recommended mileage intervals. The EFI system can be complicated to the average diyer unless familiar with sensors, their operation and how they contribute to the ecm running the EFI system. Diagnosing worn or faulty sensors can be difficult without more than average knowledge of issuing scantools, readers and interpreting sensor outputs.

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