dimanche 8 février 2015

Scenic II misfire - P0303

I have a 2004, 54 plate, grand scenic mk2, 1.6 petrol, 60k miles.



This morning after driving approximately 10 miles the engine suffered a lack of power shortly followed by the emissions caption and engine symbol being displayed. Stopping the car, the engine was obviously running very roughly.



I limped home and used my diagnostic tool to check for codes. This came up with P0303 - no 3 cylinder misfire which tallied with the symptoms.



My initial thought was a coil. There was a seepage of oil around no 2 and 3 but the coils looked normal (no discolouration etc) and the spark plugs looked good. I swapped coils 2 and 3, hoping the misfire would move with a faulty no 3 coil. The engine continued to run roughly (as expected) but the diagnostic code didn't change. I was hoping that I would get a P0302 (no 2 misfire) possibly in addition to 303 as I had not cleared that code.



I have checked this forum, but there seems a multitude of potential faults which could cause the symptoms (although most point to coils) and I would like to be able to do some diagnosis rather than changing parts until something fixes it!



Thus:



1, would my test of swapping coils be expected to swap the fault code or could it still be a faulty coil?

2, is there a way of checking whether the fault is with the fuelling or ignition side? ie can I check the spark is being produced without damaging the ECU (I've read this is a potential problem) and/or can I check the injectors are working.

3, what else should I check and in what order?



Additional info:

The fault occurred when pulling away from traffic lights on a slight uphill.

The outside temp was displayed as -1 deg c, but the coolant temp had warmed up to display normal.

The car had approximately 1/5 tank of fuel remaining and had not been refuelled since previous fill.

The fuel economy increased slightly on the 10 miles home (but I was driving slower than normal - not that I drive the bus aggressively).

The cam belt etc were changed 2 years ago.

No 2 and 3 coils were replaced circa 5 years ago.



I am tempted to spend £30 on a set of new injectors (ebay inc 2 year warranty).



Thanks for all help received.




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