Find the experience behind your next drive or repair.
W/// described replacing a throttle actuator after limp mode and fault code 2B21. The account records access beneath the intake plenum and the owner’s initial result. Later replies describe separate vehicles and different findings.
The owner reported a sudden misfire and limp mode, followed by cylinder 3 losing compression after work on cylinder 4. He later said the dealer replaced a valve spring and the car ran normally when returned.
john_s reported an immediate bank-one misfire on his 2008 E92 M3. A zero-compression result on cylinder 1 led to a broken valve spring; he later reported good compression and a return to daily driving after replacing it.
