Vortec V9 code problems
Thread Starter
Teching In
Joined: Aug 2004
Posts: 24
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From: Ventura County,California 91360
Vortec V9 code problems 98 WS6 with V9 aftercooler unit.
Misfiring on cylinder 5.
PO420 Catalyist efficiency out of range.
Mechanic says to change spark plugs from platinum to regular and reduce gap.
He also claims I need to go back to factory cats to solve my PO420 code issue.
I currently have Mac cats and headers.
Someone at the track told me Mac cats flow worse than factory.
Any other advice would be greatly appreciated.
Thanks,
Brett
Misfiring on cylinder 5.
PO420 Catalyist efficiency out of range.
Mechanic says to change spark plugs from platinum to regular and reduce gap.
He also claims I need to go back to factory cats to solve my PO420 code issue.
I currently have Mac cats and headers.
Someone at the track told me Mac cats flow worse than factory.
Any other advice would be greatly appreciated.
Thanks,
Brett
I don't know about the cat flow, if you change plugs go to NGK TR-6's. I had a problem with a missfire in cylinder 5, tried everything, different plugs, wires, coils, injectors, mass air sensor, o2's... finally had a valve job done and it fixed the problem. 
