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Hello,
I recently bought custom made stainless steel exhaust from a friend. He said that the engine light will probably came on due to the catalytic converter having more flow than stock. He was right so he also sold me ECU from his Ralliart that had that exhaust before. He also said that ECU has new map and I should buy better cold air intake system and BOV. I've tried couple pulls but at higher RPM on full throttle the engine was jerking wildly. So I bought exactly same intake AEM 21-698c as he had and instead his HKS Super SQV IV I bought GFB Respons T9033, because according my friend it needs to be venting 100% into atmosphere.
Unfortunately even I have installed all the parts he had on his car I still have engine light on (Error P0420 - Catalyst system efficiency below threshold) and sometimes around 4000-5000 RPM on full throttle engine jerks but not as much as before installing intake and BOV. I have Torque Pro app connected via OBD II bluetooth adapter and when the engine jerked I noticed drop of air to fuel ratio from 14.7 to 11.4.
When it comes to cars, I'm not that experienced so I don't even know where to look to diagnose the problem so I would be gratefull for any help.
Your friend does not understand how a catalytic converter works or how the 420 code is set. The ECU looks for either a decrease in switching rate, or the capacity to store oxygen. It has nothing to do with flowing better than stock.
Learn more how things work before you start modifying - don't listen to your friends. In order to fix something you need to understand how it works first- otherwise you are just changing parts... modifying something takes even more knowledge than repair- because you are changing it from the original design intent.
Sounds like you threw a bunch of parts on a car and did not adequately adjust the fuel/air/timing mixture, aka tune it. and now it's running like dog****.
You didn't understand what I wrote. My friend had the exact same parts I have now. He had a new map done on his car and everything worked fine. That's why he sent me his ECU with this map and told me which parts to buy to make it match. Now I'm solving why I have an error when everything should fit. The only thing that was different was the BOV brand, but it should be enough that both are 100% out into the atmosphere.
