This Mini F56 JCW has had a rough time, it has only clocked 44,000 miles and suffered a bad remap by someone unknown, and the tune was too aggressive.
The result? Damaged piston ring lands and melted pistons, requiring a new engine. The car was brought to us to remove the problematic tune, perform a thorough health check, and get it running right. While we addressed most issues, we noticed a significant running problem that we’re documenting here. This behaviour isn’t something we’ve encountered yet on the B48 or B58 engines, though it does resemble a known issue with some BMW models.
During light throttle, the engine ran super erratically, and the instability is noticeable. Initially, it sounded like wastegate fluctuation, but that doesn’t appear to be the case. On the road, the engine feels jerky, especially in fourth gear, and the exhaust note oscillates. We captured a data log to investigate further.
The log revealed the intake and exhaust cam positions fluctuated wildly. For instance, the exhaust cam showed variations from 25 degrees of advance down to 6 degrees nearly 20-degree swing which is likely causing the unstable behaviour. We also noticed significant oil pressure fluctuations, likely linked to a faulty VANOS solenoid allowing excess oil flow.