Apologies if this has been answered before but my search didn't yield an answer. I have an '05 R53 that needed a complete exhaust replacement. Based on other's reviews in this forum, I went with Milltek sport headers, catalytic converter and exhaust (no resonator). I am very pleased with the fit, finish and sound of the system. However, I have a persistent CEL (P2096). I have tried a defouler - 90 degree with a smaller intake port that worked for a couple of months but no longer. Does anyone have a recommendation for a specific spacer/defouler that solves this problem? Other options?

I live in NJ and don't know if the gasoline blend used here makes any difference.

Thanks for the help.

 

Check these out, they have mini-cats built in:

https://www.pelicanparts.com/More_In...FSO2CAT90S.htm

And a knock-off:

https://www.ebay.com/i/282282756668

 

Thanks. The Fabspeed looks well made but is a bit pricey. It may come to that though...

 

They appear to be popular among the Porsche community, so I'd hazard that they're acceptable for the rest of us. I think I'm going to put a downpipe and "stage 2" tune back on my daily VW once I pick one of these bad boys up. Even with a Vibrant Performance J-spacer, and the smallest restrictor, I still threw a CEL with a high-flow cat. I didn't want any warning lights on my daily, so I went back to factory parts.

 

I'm having CEL light issue with Milltek header also. It's because they are skimping on the platinum now? My code is P0420 though if I recall correctly.

 

Does anyone have a spacer/restrictor that's known to fit the original bung placement on the Milltek header and clear everything else in the way?

 

Update: I had installed an extension to the original 90 degree defouler. Initially, the CEL came back on - that's when I started the thread. I spoke to Fabspeed today. The rep suggested that the Fabspeed unit would not solve my problem and he put forth that he felt it was likely the cat had failed (he suggested that perhaps Milltek used an inferior cat element) and that I should consider purchasing a replacement bare cat from them and have it welded into the header.

I was highly skeptical of that diagnosis for several reasons: Milltek has a good reputation; the Cat-header unit has a significant warranty period (that I am still well within); the engine is running as well as it ever has. So, I cleared the codes and took a drive during which I measured the O2 sensor output voltage using the OBD-LinkMX+ Bluetooth OBD2 reader and OBD Doctor software. The graphs looked just like the text book examples: upstream sensor oscillating between 0.1-1.0V and the downstream sensor relatively flat with occasional fluctuations corresponding to gear shifts, braking, etc. The cat is clearly performing as it should. No DTC codes are present.

I don't know if my problem is solved for a day, a few months or forever. The Fabspeed unit may work well and if my problem returns, I may try it. With respect to clearance, the 90degree unit looks like it should work fine and the anchor nut will allow an installation such that the sensor is slightly tilted up to reduce any condensation from staying on the sensor element.

 

FWIW, that fabspeed unit / any secondary O2 sensor spacer is typically useful for getting rid of a P0420, which I admittedly overlooked based on your initial question. Are you using OEM (original or replacement, either way) / Bosch O2 sensors, or have they been replaced with cheaper aftermarket-branded ones?

I've had similar issues before (admittedly with the rear O2 sensors) on other cars, and have received parts that sent a "usually-correct" signal but would ultimately still throw a fail code.

Audihere - Can't answer your question directly, but some basic measurements taken on your vehicle referenced against part dimension specifications will produce the answers you require.

 

To answer your first question, I had replaced the O2 sensor only a couple of months before I replaced the cat. It is a NGK sensor which were OE on my car.

I drove the car again today and the CEL is back on with the P2096 code. It is both a current and pending code so even if the code is cleared, the pending code lights the CEL as soon as the car is started.

I am beginning to think that the sensor is fouled and needs cleaning or needs to be replaced despite the voltage readings that suggest it (and the cat) are working properly.