P0303 Misfire

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02-12-2018, 12:39 PM

trwtestengineer1

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P0303 Misfire

Have a 2007 R56. Getting code P0303 cylinder #3 misfire. Now a 4 banger is easy to tell if misfiring. Not the case, runs great. Replaced plugs (just to be in good form!) 60,000 MILES. Swapped coil packs between #1 &#3, still the same. Traced wiring harness, all good. Any ideas?? thx.

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02-12-2018, 03:20 PM

AnOldBiker

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Welcome to the forum

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02-12-2018, 03:43 PM

Whine not Walnuts

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Going to move you to the Gen2 Stock Problems/Issues area. Some of us have the older Gen1 and have no idea about those fancy newer models.

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02-12-2018, 04:54 PM

AZdsrt

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Could be a zillion different things. I'd first check for carbon deposits on the intake valves..

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02-13-2018, 08:13 AM

nkfry

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Quote:

Originally Posted by trwtestengineer1

Have a 2007 R56. Getting code P0303 cylinder #3 misfire. Now a 4 banger is easy to tell if misfiring. Not the case, runs great. Replaced plugs (just to be in good form!) 60,000 MILES. Swapped coil packs between #1 , still the same. Traced wiring harness, all good. Any ideas?? thx.

Is this a Cooper or an S?

Have you done a compression test yet? What are the results?

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