Audi S4 B6 B7 V8 Misfires on Cylinders 5–8 Bank 2 Running Hot Clogged Catalytic Converter Piggies

Описание: This Audi S4 4.2 V8 (B6 & B7 – 2004 to 2008) is experiencing misfires on cylinders 5, 6, 7, and 8 (Bank 2). Coils and spark plugs have already been swapped and ruled out, yet the misfires remain.

Using a laser infrared heat gun, I checked exhaust temperatures at the flex pipes, and Bank 2 (driver side / Cat 1) is running significantly hotter than Bank 1. The temperature difference is consistent and points directly to a restricted or clogged catalytic converter, not an ignition or timing issue.

On the Audi S4 B6/B7 4.2L V8, a clogged catalytic converter creates excessive backpressure, raises exhaust gas temperatures, and commonly causes bank-specific multi-cylinder misfires. This failure mode is rarely discussed online, where misfires are usually blamed on coils or timing chain guides, even when those components test good.

The proven fix on these cars is the well-known “Piggies” mod — gutting the factory catalytic converters to restore exhaust flow, lower temperatures, and eliminate bank-specific misfires.


Audi S4 B6/B7 (2004–2008) misfires on Bank 2

Cylinders 5–8 misfiring together

Coils and plugs ruled out

Infrared exhaust temperature testing

Evidence of a clogged driver-side catalytic converter

Why piggies are often required on higher-mileage or heat-soaked S4s

If you’re diagnosing persistent misfires on one bank of a B6 or B7 Audi S4, exhaust restriction should be high on the list.

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