Independent technician Baz Meredith from his self-titled channel tackles an Audi S4 3.0 V6 misfire triggered by a botched DIY repair that masked a far more destructive exhaust issue.
The job began after the owner attempted a PCV valve replacement without locking the inlet manifold tumble flaps into service position, severely bending bank one’s flaps and wedging them shut.
After replacing the damaged manifold and having the fuel injectors ultrasonically cleaned and resealed by United Diesel, Baz rebuilt the top end using a vacuum rig to hold the flaps open.
However, the misfire returned immediately, accompanied by an intake flap code. Compression and ignition tests passed, prompting Baz to investigate exhaust backpressure.
Inspecting down the exhaust revealed a completely melted catalytic converter, which was choking the V6 and forcing exhaust gases backwards into the inlet, throwing the intake flaps out of place.
