Removing O2 sensor J extension bung on FI LTH
 

so i went to a tuner because my car have this code p0300 for a while now and recently the car is running really bad and misfiring a lot. This p0300 code started when we installed the FI LTH and so i went to the tuner because this is what they recommend to me and now the tuner still cant fix the issue and told me i need to get rid/remove the extension bung or J bung that comes with the headers and have the o2 sensor bolted directly to the pipe. Is this going to be a fix to my car or not?

Isn't there 2 bung locations?

Sensor 1, direct exhaust flow. (This is what the ECU uses for adjustments)
Sensor 2, extension bung to defeat CEL.

If your tuner doesn't know this, get a different tuner.

Get another tuner. Seems they are not very good. I see you are in California. I would Sebastian at Specialty Z to tune it.

:iagree:

I've only ever heard positive things about Seb at Specialty Z

the thing is i already paid him $650 i will go back there today and have him look at it again and if he cant still fix it hopefully he can still give me back my money.

You're risking damage to your precious Z every time you let that tuner touch it. Request a refund (good luck) or just cut your losses and move on would be my recommendation.

This.

Ok so it turns out to be a bad front O2 sensor and now i need a new one. I dont know which one to buy the upstream or downstream o2 sensor? And what brand is a good one with a good price and where to buy them? Thanks in advance

Up=stream is the front...usually the rear one's tuned with.
They can be damaged if you used impact wrenches to remove bolts,etc..when removing/installing lth's

Also,i thought a po300 was random cylinder mis-fire?

Bosch is pretty durable...but other people make them/a bit pricey for the up-stream(front) one's.....usually the rear's are turned off during a tune-to prevent a cel

https://uploads.tapatalk-cdn.com/201...836a00071e.jpg
Upstream is in the header & not the J pipe bung


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What do you think about the brand NTK or Denso?

either should be fine...Denso may be oem/ like spark plugs,
NTK is NGK's brand...haven't had to replace any yet @ 77,500mi.
just don't us impact wrenches on exhaust & be sure exterior of sensor's are clean...around wiring.

Which sensor is bank 2?