jasmineagle18

Mini Cooper Uneven Engine Running

My 2004 Mini Cooper is exhibiting uneven engine running. The check engine light is illuminated, and error codes are stored in the memory. The car also experiences jerking during acceleration, almost like it's misfiring. I suspect an exhaust leak somewhere along the system, as that seems a common issue on these. Thoughts?

4 comment(s)

Rough idle and jerking on acceleration sounds familiar. I had a similar issue with my old Saab 9-3. Turned out to be a vacuum leak throwing off the engine's air fuel mixture. Have you checked all your vacuum lines for cracks or disconnections? Also, have you had a look at the readings coming from your crankshaft sensor? Are you getting any specific codes related to the oxygen sensor? Did you change your air filter or spark plugs recently?

Vacuum lines seem okay at first glance. Crankshaft sensor seems to be functioning within spec, according to the OBD scanner. The stored error code points towards a general 'mixture malfunction'. About the oxygen sensor, is there a way to test it without specialized equipment?

Yeah, a general mixture malfunction often points to air leaks post MAF. As for the oxygen sensor, a multimeter can give you a rough idea if it's oscillating, but it's not foolproof. Given the code and your suspicion of an exhaust leak pre-cat, it's probably best to get it smoke tested by a professional to pinpoint the exact location. I bet that's your issue. Good luck, let us know how it goes.

Confirmed exhaust leak was the culprit. Replaced a section of the exhaust system and the upstream oxygen sensor while they were at it, as it was reading funny. Seems to have resolved the uneven running and CEL. Cost me 265€ all in. Thanks for the insight, mate.

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