P0303 Misfire

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Feb 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.

Feb 12, 2018 | 03:20 PM

AnOldBiker

4th Gear - An Official NAM Greeter

Joined: Sep 2017

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Welcome to the forum

Feb 12, 2018 | 03:43 PM

Whine not Walnuts

OVERDRIVE

Joined: Mar 2013

Posts: 5,489

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From: Fuquay Varina, NC

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.

Feb 12, 2018 | 04:54 PM

AZdsrt

6th Gear

Joined: Jun 2013

Posts: 1,567

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From: Scottsdale, AZ

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

Feb 13, 2018 | 08:13 AM

nkfry

Vendor - Detroit Tuned 15 Years

Joined: Jul 2014

Posts: 1,859

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From: Clawson, MI

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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