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Hi, Installed the AP High Flow cat headers, after driving for less than 10 miles got Code P0421 and P0431, Not going to tune the car. what are my options, wondering if Universal O2 Spacers with Catalytic Converters will help.[h=1][/h]
 

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Hi, Installed the AP High Flow cat headers, after driving for less than 10 miles got Code P0421 and P0431, Not going to tune the car. what are my options, wondering if Universal O2 Spacers with Catalytic Converters will help.
You're a few steps a way from that. First, clear the codes and see if they come up again tomorrow (or after the car cools). Those codes are for warm-up and efficiency on one side of the engine, so it could also be that sensor is faulty and the car might not throw a code if replaced. Many here have high-flow cats without throwing code, as you undoubtedly know. Problem with the spacers is you will likely fail a visual emissions test, if your state has them.....
 

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You're a few steps a way from that. First, clear the codes and see if they come up again tomorrow (or after the car cools). Those codes are for warm-up and efficiency on one side of the engine, so it could also be that sensor is faulty and the car might not throw a code if replaced. Many here have high-flow cats without throwing code, as you undoubtedly know. Problem with the spacers is you will likely fail a visual emissions test, if your state has them.....
Thanks, will do. By the way we dont have emission test, I have fabspeed supercup exhust on the car, also installing IPD Plenum with TB, If i tune the car will i void the warranty, Car is 14 Boxster S
 

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If i tune the car will i void the warranty
That's not a black-and-white situation. The warranty would be voided if -- if -- the tune had something to do with the failure. While Porsche might try to claim the tune would void it some other reason, it is not clear they can......
 

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That's not a black-and-white situation. The warranty would be voided if -- if -- the tune had something to do with the failure. While Porsche might try to claim the tune would void it some other reason, it is not clear they can......
No Luck, Cleared the code back again after driving around 10 miles
 

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No Luck, Cleared the code back again after driving around 10 miles
Well, I'm pretty sure with a Cobb tuner you can reload the stock map and they would never know you had tuned the car. You might also just want to put the stock headers back on as AP headers definitely cause a CEL and it won't go away on its own...Mine certainly hasn't.

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You might also just want to put the stock headers back on as AP headers definitely cause a CEL and it won't go away on its own...Mine certainly hasn't.
Interesting. My CG headers never threw a code and most folks here -- if not all -- have had the same luck.

OP, sounds like it's time to try the 02 spacers.....
 

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I guess that someone has checked the fit of the O2 sensors to the headers to see if they aren't leaking and throwing codes. It may be a leak at the heads or elsewhere (pin hole in weld?).

The other issue is the O2 sensors have an adaption that needs to be reset when replacing them.

if you recall, in the 1980s when O2 sensors first came out, they lasted 30K miles. Later on they moved them further away from the manifolds and reduced cooking of the sensors and they got to 50K mile life. To get to the 100K mile life, they characterize the aging process and the engine computer (DME) runs a correction factor in the readings based on the age of the O2 sensor before acting on them. When you get to 20K or more miles and change O2 sensors, you have to reset what is known as the Lamda adaption via the PIWIZ.

Last summer, my car melted two sets of headers. I had figured out that the rear mufflers were plugged, but that was a byproduct of the real problem. Dyno work with a intentionally leaking exhaust showed that i regained lost HP, but the O2 sensor readings were terrible, running 11.2:1. I replaced the O2 sensors and then reset the Lamda adaptation and then the car ran 14.2:1 at low power/idle and ran 13.2:1 at full load, fixing the problem.

The original problem in my case, was I used track gas from a pump marked unleaded, but it was not. It contaminated the sensors and caused the car to run way rich which caused the muffler plugging and then the cat meltdowns.

V6
 

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Discussion Starter #9
I guess that someone has checked the fit of the O2 sensors to the headers to see if they aren't leaking and throwing codes. It may be a leak at the heads or elsewhere (pin hole in weld?).

The other issue is the O2 sensors have an adaption that needs to be reset when replacing them.

if you recall, in the 1980s when O2 sensors first came out, they lasted 30K miles. Later on they moved them further away from the manifolds and reduced cooking of the sensors and they got to 50K mile life. To get to the 100K mile life, they characterize the aging process and the engine computer (DME) runs a correction factor in the readings based on the age of the O2 sensor before acting on them. When you get to 20K or more miles and change O2 sensors, you have to reset what is known as the Lamda adaption via the PIWIZ.

Last summer, my car melted two sets of headers. I had figured out that the rear mufflers were plugged, but that was a byproduct of the real problem. Dyno work with a intentionally leaking exhaust showed that i regained lost HP, but the O2 sensor readings were terrible, running 11.2:1. I replaced the O2 sensors and then reset the Lamda adaptation and then the car ran 14.2:1 at low power/idle and ran 13.2:1 at full load, fixing the problem.

The original problem in my case, was I used track gas from a pump marked unleaded, but it was not. It contaminated the sensors and caused the car to run way rich which caused the muffler plugging and then the cat meltdowns.

V6

I haven't replace the O2 Sensors, car has 16k miles. I installed the O2 spacers yesterday. drove the car for over 100 miles and no CEL. i was getting CEL after driving around 5 miles. i guess it worked. the only problem i have now is that the car is extremely loud, even worse when the Top is down. i guess i have to replace my Fabspeed supercup race exhaust, i'm going to install the IPD plenum next week, i hope i won't have any problem. i heard from some 981 owners that they got CEL after installing IPD plenum.

02_sencor.jpeg
 

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Before I upgraded my 3.4L to a 3.8, I had the IPD plenum with 82mm throttle body and experienced CELs that went away over time. Some have tried to explain this as the DME adapting to the air flow conditions, but I think it is mechanical.

The CELS that I experienced were implausible air flow at idle. This is caused by, in my opinion, the larger throttle body - given the same gap at closed throttle, has 10 percent more area to leak past the throttle plates and that causes the CELs (82mm vs 75mm TB). With some, the CELs go away, some never experienced it, some it does not go away and a new TB fixed the issue.

My opinion is that the throttle plates are sprung and slam closed against a mechanical stop. As the stop wears, the plates close a bit more over time, until the air flow at idle falls below the CEL threshold. I think there is manufacturing variation in the gap between TBs and some never close enough and a replacement TB works. But that is just my speculation and handling the actual throttle bodies.

V6
 

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I am running sport cats and have noticed quite a bit of carbon buildup on the post-cat O2 sensor. I am getting the old P0431 CEL for Bank 2 only. Thoughts?
 
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