Car won't start one week after installing headers
 

Hi everyone,
So pretty much last Friday I had a shop install these catless EL headers. When I got home from the shop I did the stage 2+ tune from my OFT. Car was a lot of fun to drive and drove fine all week. This morning as I was coming back home, I was doing a 3 point turn and I braked.
As the car came to a full stop the engine just cut off. I turned it off and tried to turn it back on but no luck. I got a boost because I thought that was the issue but no. When I was under the hood I smelled a faint burnt smell, wasnt sure if that was from the header but when I looked I saw my 02 sensor seems to be burnt. Sorry if the picture isn't clear enough. I did search these forums but I found several different threads with people who had a similar problem to mine. I also found several different answers.
So I am no mechanic, but if the car won't start and I notice the 02 sensor is damaged, it would seem like I need a new 02 sensor. But before I spend money, I have a few questions: has anyone heard or had this issue before? Why would the sensor go bad, is this something that just happened or is it the shops fault? Im praying its just the sensor and nothing more like the wiring or I dont even know what.
Thank you all in advance for any help.

Edit: Car is a 2014 BRZ, added Skunk2 EL Headers

I don't see anything that would convince me (from the picture alone) that the O2 sensor is bad. Anyone know if the car will run briefly with no o2? Could help for testing if you just unplug it and see what happens.

Does it crank? Any other symptoms? Check engine light?

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I'm with you here. I've left an O2 sensor unplugged on occasion, it'll throw a code and stumble, but I've never had a car die due to emissions equipment. Worst case, limp mode.

Side note, that bung looks flat wrong, almost like the shop chopped the entire bung and sensor off before swapping. What header is this?

What's ur car year and model? Are u able to check the fuel trim on OFT? Cuz brz/frs they adjust the AFR through reading O2 sensors and send it back to the ecu to do the adjustment. I once had a catless uel header and sometimes it won't start well because of the ecu thinking it run too lean based on what o2 sensor reading. Then, it will flood the engine with too much fuel thus it will crank but won't turn over. That's my guessing ofc.

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If it wouldn't start because it was too lean, why didn't you just richen it up?

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The o2 senor tricked the ecu thinks it's too lean and enriched it too much. Thus, it did richen it but too much. In fact, it wasn't lean. It was just because of the catless header.

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Really? So its not the 02 sensor? It literally gives one crank and then just gives up, no check engine light

Im guessing the bung is that lip around the sensor? Thats why I thought it went bad to be honest, but it seems that the shop did that? This was a skunk2 EL header

Its a 2014 BRZ, sorry I should have said that in the original post

One crank then no crank? Any sputter? Or does the engine just spin? Definitely not o2 since there isn't anything for the sensor to measure until the car is running. Almost sounds like a battery or ground issue. Can you test your battery? Are there any damaged wires anywhere? Does you're fuel pump work? Can you test for spark?

I know it's a lot of questions but diagnosing a car is pretty complex. Especially over the internet


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Them your o2 sensor wasnt reading correctly. Or you had a big leak upstream from the sensor. If it's not reading what is actually there, then it's not doing it's job. Additionally, your o2 sensor doesn't do anything during cranking since the engine isn't running yet, there's no exhaust to measure. Sounds like your tune was just bad. Or there was another problem entirely. I haven't had cats in years. On the FA20 or now my LS. Never had an o2 cause a no-start. I've had numerous other things cause no starts. But never an o2 sensor

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Don't worry I welcome the questions as they can help narrow the problem down. Battery was changed in May actually so its fairly new. I can look again tomorrow for any damaged wires. Thank you.

What about the other questions? How exactly does it crank? Crack and sputter? Crank with no fire? Crank then no crank? Does it reliably crank right away when you turn the key? Any other symptoms at all?

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Fuel pump works, it gives one weak crank and sputter then just gives up, I will send a video tomorrow, its a push start btw, no engine codes no nothing, boost didn't help start the car. I can get the battery tested but like I said I just bought this battery in May.