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View Full Version : *HELP NEEDED* B6 S4 4.2 Cabriolet MISFIRES HARD



FourRingsC6
04-22-2017, 07:36 AM
Hello everyone
My first post on here in hopes to find solution or some guidance on troubleshooting my recently purchased B6S4 cabrio.

CAR - 05 S4 4.2 Auto 133k
When I bought the car few days ago it was starting with no issues from the first crank but it was running very rough. Scan showed P0300 /P0301/P0304/P0302/P0307.
Car was misfiring almost on every cylinder but ran. (Rough)
Strange thing was that when RPMs would go up to 2500+ the check engine light would stop flashing and car performed like it should. I drove it home with no issues. It only starts to misfire hard when coming to a stop.
I replaced all 8 plugs to NGK iridium yesterday and it did not fix the issue. I am going to swap all coil packs from my C6A6 4.2 and see if thats helps at all.
I don't know much about these 4.2 engines so I'm hoping someone could help me troubleshoot it. BTW i read that sometimes intake manifold bolts get lose so I tighten them up yesterday and nothing happened.


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Jafa
05-29-2017, 10:07 AM
Carbon build up intake maybe.