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Discussion Starter · #1 ·
Bought a fault code reader today. It's coming up with PO304 Cylinder 4 misfire + PO420 Catalyst efficiency below threshold.
I'm pretty sure the rover 25 cat i put on has caused the misfire coz that's about the time the light came on (obviously causing both codes to appear).
But does anyone know which cylinder is number 4? Does it go by firing order or left to right?
Cheers for any help in advance guys.
 

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Boost ftw!!
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Discussion Starter · #4 ·
Cheers guys.
Will give it a check over tomorrow. Looks like i need a new cat though. How are the 2 faults linked though. I read that a dodgy cat can cause the misfire.
 
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