Nissan Qashqai 2008 fault code P0303 Cylinder 3 misfire

Question

Unfortunately this has popped up on my partners J10 Nissan Qashqai 2008, I recently had a P0420 fault code although after replacing the o2 sensors it seems to have disappeared after clearing now being replaced by a P0303, Car has been sitting for 2 weeks whilst I changed oil,Brake pads and o2 sensors, Decided to take it for a run today for 30 miles and had this sitting in the pending codes twice even after clearing. So I’m expecting it to show the EML at any moment.

Anyone have experience with this? Did check through the service manual which mentioned to check the o2 sensors along with a bunch of other stuff, Can’t see it being the o2 sensors as the readings seemed within normal tolerances.

Having experienced similar issues in previous cars I know this can get really costly, So I’m after some advice on probable causes first rather than going start to a garage to get some bs like a timing sync issue.

Answer 1

If it’s easy to get to can’t hurt changing the plug. While you’re there you can test the coil with a multimeter. Also seen people swap the coil from say #1 to #3 and vice versa. If the misfire moves to #1 it’s a bad coil. Injector could be at fault as well, though from my experience it’s not nearly as common. Hope this helps.

Answer 2

Very common. The usual thing if you have the tools is swap coils and spark plugs between good and bad cylinders. Then see if the misfire moves. Usually I'd do a quick compression test while plugs are out, saves a little diag time if the misfire doesn't move.

But the basic thing is you don't have to throw parts at it or replace anything until you're sure. Move things around, clear the code, then drive it and see what comes back. If coils and plugs and compression is good, the next thing would be move injectors and check again.