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Really rough running!!!

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Hi all, I'm new to the forum.  Have had my 2005 911 996 Turbo S for 4 years with no issues and have only put about 1500 miles per year on it.  (In Hawaii and its a small island:-))   It has run perfect until a few weeks ago when things went really rough.  Cleaned and then replaced the MAF with no change.  Ran the gas down low and then put in fresh gas--no change.  Changed both the Air and Gas filters (easy stuff first), no change.  Bought a Durametric and have been tinkering around with it.  Codes I'm getting are P0153 O2 sensor aging Period bank 2, P0133 O2 sensor aging Period bank 1 and P0455 Tank vent system major leak.  When the engines cold its hard to start and idles rough, when it warms up it idles OK but then has big hesitation up until around 3000 rpm when it all smooths out again.  Don't see or hear any obvious vacuum or vent leaks.  (I just replaced the gas cap and also no change)    I'm thinking my next step is both O2 sensors upstream of the Catalytic?   Also, if I do that can I get to them with the "special tool", or do I need to take the back of the car apart.  (I have a lift so thats not the end of the world)


Looking for comments and thanks in advance!!!



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Yeah, could be the O2 sensors.  Lots of possibilities, but you'll need to do a pressure check first off. Not sure when your last plugs and coils were replaced?

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Thanks for reply!!!   Are you talking about a fuel pressure test?    I've never done the plugs or coils and it has 58000 miles so if I do have to take off the bumper and intercoolers I'll definitely do them.  I don't believe their my issue however since nothing shows up as a cylinder misfire on my CEL or Durametric.   (My CEL has never come on)



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No not a fuel pressure test, but the entire sealed boost pressure test for leaks.  like this, though there are simpler ones. 


996 Turbo Forum - Boost pressure leak testing, simplified... - Boost pressure testing on our turbos is pretty critical to maintaining performance. Not uncommon at all to have some small and medium size leaks and not know it. It won't throw a CEL, and you'll often still...

You definitely should replace plugs and coils.  Get the upgraded 997 coils.

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Statman, got it and thanks!!!   I've also ordered a smoke machine and will check out the vacuum and vent systems to see where that leads.  Coils and plugs are also in the plan.



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