Hi guys, here's cold start and cruise with my new injectors. Can someone tell me what's going on with my tune? I think I might have a bad O2 sensor. Going for a dyno tune soon.

 

not to ask a dumb question but im assuming that you dont have rear O2s anymore and you are refering to your front O2s correct? have you scanned for any fault codes? from my experience (hyundai technician) O2s usually dont just bite the dust unless they are highly fouled up from carbon or excessive heat, or they have an O2 heater circuit fault code.

 

No trouble codes. Yes, I have front sensors only.

 

With no trouble codes i would assume your O2s are fine. You can pull them and check to see if they look fouled up or abnormally worn. If everything ran fine until you put your new injectors in I would point to your new injectors being the culprit. If you still have your rear O2 sensors lying around you could swap those with the the ones you currently have in and see if the problem persists. If it still does then I'd say that the O2s aren't your problem.

 

I got a great deal on new O2 sensors today and installed them. The O2 voltages are now similar, the STFT's are as they should be but the LTFT's are still out by a consistent 5 percent from each other. I wonder why? Maybe a small exhaust leak?

 

could be an exhaust leak. did u check your exhaust system for any leaks? O2s are an emissions component not the powertrain. they are just gonna tell your pcm whether your cats are doing there job of burning up the rest of the unused fuel, and adjusting the air/fuel ratio accordingly to get it to that predefined spec. but, with cats removed and only running front O2s, with tuning involved, i have no idea. have you driven it around and put some miles on the new injectors and new sensors to see if it brings that long term fuel trim to where it should be?

 

Do you have cats ?

Do you have a broken manifold stud that could be creating a pre o2 sensor leak ?

 

LTFT's take a while to change. Did you reset fuel trims after installing the new O2's?

 

Yes, I reset the fuel trims and it ran like garbage for a while. Once it warmed up after a minute it ran ok but I was still getting the split. I checked for exhaust leaks and found none. I will run another scan tomorrow. I do have professional help coming this weekend.

 

Do you have the headers/exhaust on it now, or still the stock mani's & Y? Have you checked for exhaust leaks? I like using a stethoscope to find them, works great. Besides the new injectors, were any other changes made?

When you reset the fuel trims, and it ran like **** on the restart, it tells me that the tune is off. The O2's don't get used for fuel-correcting until it enters closed loop, so I don't really think it's an exhaust leak issue. Maybe a mis-fire or a vacuum leak is messing with your O2's and fuel trims. Lots of possibilities here. Hope it isn't too bad for you to track down.