Randy_Baton Posted October 3, 2022 Share Posted October 3, 2022 (edited) My cars failing its MOTfor emissions, the garage dont know what the issue is but think it might be my cobra back box. It's only 6 years old new from cobra. I've used another garage before who were great and they are also a powerflow custom shop. So I'm going for to take it there for a second opinion and i guess may end up with a powerflow back end. Don't want anything sounding too severe. I like my cobra, except for the 3-4k rpm drone! They do an off the shelf back box delete, but won't the lack of back box make it really loud? They do custom work as well, so they can hopefully make it sound as quiet as I want but that's a bit hard to judge isn't it... Edited October 3, 2022 by Randy_Baton Quote Link to comment Share on other sites More sharing options...
davey_83 Posted October 4, 2022 Share Posted October 4, 2022 The only way the exhaust post cats would cause an MOT failure is if it had a noticeable exhaust leak, if it doesn't it's unlikely to be the exhaust. 1 Quote Link to comment Share on other sites More sharing options...
Coz@TORQEN Posted October 4, 2022 Share Posted October 4, 2022 As Davey said, there is little to no chance that it's an issue with your catback system unless you have a huge exhaust leak. I would start looking at the cats and seeing what kind of shape those are in. If the cats are knackered, you'll definitely be failing MOT, are they the original Nissan ones? 1 Quote Link to comment Share on other sites More sharing options...
Randy_Baton Posted October 4, 2022 Author Share Posted October 4, 2022 (edited) Yes they are the OEM ones. I spoke to the owner seemed way more knowledgeable then the person i spoke to on the phone yesterday, he thinks its an air leak pre cats. Its a high lambda fail so too much o2, and as such shouldn't be a CAT issue? They smoke tested it with a wet rag in the exhaust and plugged a few leaks which brought it down, but its still a fail. Oil hasn't been changed for 3 years but its only done ~5k in that time.. I've hardly had to drive since lockdown started. I usually get it done as part of the MOT, so I'll get the next garage to do that first. It also needed the spark plugs and air filter changed (I just did the air filter and the old one was fine), presume sparks wouldn't be an issue (or they'ed show up in the codes). They are getting reads from the sensors so don't think its that, but could they still be dodgy? A couple of week ago my battery went flat and when trying jump start it it blew up my portable jump starter. I changed to fresh car battery but have been having an issue with the negative lead being too loose and disconnecting (the nuts is as tight as i can make it). Could any of that have fried something? The garage i'm taking it do tunes etc, so could they tune the car to use less o2 or more fuel. or is that dumb? Edited October 4, 2022 by Randy_Baton Quote Link to comment Share on other sites More sharing options...
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