Lumpy warm-up

My 2009 Nissan Qashqai has been gas-converted for the past three years. Last year, it developed a slight lumpiness and eventually the

EML came on fully, after many weeks of flashing for a minute or so then going out. My handheld scanner showed an error code of ‘0302’, so I put in a new set of plugs, which required the removal of the inlet manifold. The error message changed to ‘0300’ and I put in a set of coils, but the problem remained. After taking it to a local garage for a very expensive cylinderhead gasket job, it came back with the same problem and showing ‘0300’.

The symptoms are the same from every cold start. The car will start smoothly, then, after a couple of minutes, the EML will start to flash and will stay on (although it has occasionally been known to stay off). The car gets lumpy during this warm-up period, but only very occasionally will it seem as if a whole cylinder has gone down, usually it feels like it’s running on 3.5 cylinders. When totally warmed through, the car behaves impeccably for 90% of the time, but will revert to the lumpiness for the remainder. The problem is the same whether I am running on petrol or gas.

If I cancel the error message when cold, the EML will flash as normal and go off till the next day. If I cancel it when hot, the EML will stay off for as long as the car stays hot, then will go on at the next cold start. John Brown

The code ‘0300’ refers to a random misfire and the code ‘0302’ indicates a misfire on number two cylinder. Inlet manifold leaks rarely cause cylinder specific misfire problems, so you should look first at the ignition system.

I am hoping that the garage that went to all the trouble of removing the cylinderhead also properly checked the condition of the valves, but if you are in doubt about this then a compression test or cylinder leak-off test would be advisable. Assuming this is not the case, or you do carry out these checks without finding a problem, I would suspect the coil pack is failing. Although I appreciate this is not a simple job on the Qashqai, it would be worth swapping the coil packs. I would swap coil packs two and three to see if you change the code from ‘0302’ to ‘0303’, which would confirm the coil pack failure.

If the code does not alter and you have eliminated the possibility of a burnt valve seat, then you are either looking for a break in the wire between the coil pack and the ECU, or a cam follower sticking when cold. As your vehicle has a gas conversion and the problem arises on both fuels, you should be able to reject the possibility of an injector fault.