Mr_turbo Posted January 31, 2020 Share Posted January 31, 2020 Hello, im looking for some advice. I’ve just fitted a cobra sport cat back system to my STi hatch and had it mot’d. Unfortunatly it’s failed the mot due to the lambda sensor. Has anyone else suffered from this? Does anyone know how to fix it? Cheers. Quote Link to comment Share on other sites More sharing options...
mattiekane Posted January 31, 2020 Share Posted January 31, 2020 Hello, im looking for some advice. I’ve just fitted a cobra sport cat back system to my STi hatch and had it mot’d. Unfortunatly it’s failed the mot due to the lambda sensor. Has anyone else suffered from this? Does anyone know how to fix it? Cheers. What do you mean by "failed it's not due to the lambda sensor"Was the lambda results out on the emission test, or the lambda sensor not fitted?Loud pipes save lives Quote Link to comment Share on other sites More sharing options...
Mr_turbo Posted January 31, 2020 Author Share Posted January 31, 2020 hi yeah, the lambda results were out on the emissions. It is defiantly still fitted. cheers. 1 Quote Link to comment Share on other sites More sharing options...
mattiekane Posted January 31, 2020 Share Posted January 31, 2020 So, there is potentially 2 main reasons for this, the lambda sensor is goosed, or the sports cat can't bring the emission down far enough to meet what you need. The 1st lambda sensor is there to read what level of O2 is left in the emissions after the combustion cycle and relays this to the ECU so it's can use the information (along with other information) to adjust the amount of fuel given to keep the correct lambda reading. The second lambda sensor(after the cat) is there to cross reference with the first lambda sensor and ensure the Catalytic converter is doing its job and bringing levels down to the required level(to pass an Mot).The 3rd reason could possibly be a air/fuel issue.I'd suggest refitting the original cat and getter retested, by far the cheapest option to startLoud pipes save lives Quote Link to comment Share on other sites More sharing options...
Mr_turbo Posted January 31, 2020 Author Share Posted January 31, 2020 It’s not a turbo back system I put on her so the cats are still fitted. Only went for the non res system which is the only difference. Dono if this helps ya or not. Cobra also state that unless you opt for a decat it should pass emissions. I also don’t have any fault codes coming up. I don’t know that they will if the sensor is goosed or what. 1 Quote Link to comment Share on other sites More sharing options...
mattiekane Posted January 31, 2020 Share Posted January 31, 2020 It’s not a turbo back system I put on her so the cats are still fitted. Only went for the non res system which is the only difference. Dono if this helps ya or not. Cobra also state that unless you opt for a decat it should pass emissions. I also don’t have any fault codes coming up. I don’t know that they will if the sensor is goosed or what. Yeah definitely skimmed through your first post a bit quick [emoji2361] cat back should make zero difference then, I had a similar thing that turned out to be a mixture of a cheap lambda sensor fitted and timing out slightly.When was it last serviced and does it get an occasional "tanning"(a good boot)?Loud pipes save lives Quote Link to comment Share on other sites More sharing options...
Mr B Posted January 31, 2020 Share Posted January 31, 2020 without having checked emissions prior to fitting the cat back you only assuming the cat back causing the issue . Have you got printout from MOT emission test . Simple things like exhaust leak, damage sensor/wiring and on systems where lamda position in replacement system can effect function . Best way attack this is visual inspection and graphing pre and post lambda sensors as the response and readings generally tell you likely source of issues if nothing obvious from visual inspections . 1 Quote Link to comment Share on other sites More sharing options...
Mr_turbo Posted January 31, 2020 Author Share Posted January 31, 2020 I don’t think the cat back is causing any issues, I thinks it’s a damaged/faulty sensor. I’m not sure if they’ve even been replaced before I had the car, I’m guessing not as the standard exhaust has been on the car until today and it’s a 10 plate. There’s no leak on the system as the garage who fitted it said themselves. I’ve got a call with Subaru tomorrow to ask about replacement sensors, hopefully that’ll fix the problem. Quote Link to comment Share on other sites More sharing options...
Mr B Posted January 31, 2020 Share Posted January 31, 2020 the denso sensors in subaru packaging are silly money, if need sensors source them as Denso brand, diagnosing wiser than throwing parts at it in high component cost scenarios like this . Quote Link to comment Share on other sites More sharing options...
Mr_turbo Posted February 1, 2020 Author Share Posted February 1, 2020 Been Running the car since half 8 this morning, put some injector cleaner in it and had it for a hard drive. Managed to get the local garage to stick the probe in the exhaust and it’s still not meeting the levels for the lambda. Got use of the garages ramps to get the sensors out and give them a clean up. Hopefully that works, otherwise it’s gonna be an expensive fix. Quote Link to comment Share on other sites More sharing options...
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