Reply To: 2010 GV250 EFI missfire
I just bought a 2010 GV250 EFI and the rear cylinder has a misfire. I have replaced both sparkplugs and verified they have spark and I have even swapped the injectors. No matter what I do the misfire stays on the rear cylinder. Idle rpm is also at 5000 while warming up and even tho the throttle body is closed. I don’t know how to fix it.
Unplug your O2 Sensors first front see how it behaves then plug it back in and unplug the rear one see how behaves. If it improves with 1 unpluged you know ones bad if you unplug both and it runs fine gotta further diagnose. there’s also a small black Idle speed control valve on the bottom right of the tank by the fuel hose. Your airbox will have the airhose that feeds that vacumm circuit you can plug that and see if your butterflies are truely “closed” or not.