Faulty O2 Sensor?
 

Have my turbo kit installed minus injectors, computer and a tune. Not building any boost. HOwever when i start my car up the air/fuel ratio reads 14.4 in a cold start, it used to sit at 13.6. When under full throttle it used to be at 12.8-13.2 now it is at 14.1. Can anyone guide me in the right direction, could it be the sensor for the air/fuel gauge or the O2 sensor?

^^^^^^heres your problem. ^^^^^^^^^^

without a tune you may want to stop driving it otherwise you will need to add a engine rebuild into your budget.

Even if im not building any boost? Everything is put together but the wastegate is open.

you hooked up your boost source to the wastegate incorrectly. the boost reference line goes to the bottom nipple on the wastegate, not the top nipple. the top nipple is a vent. if you run your boost/vacuum line to the top nipple then the wastegate will stay open.

Ok i wasn't clear enough. I am purposely not building boost right now because i do not have a tune, injectors etc. installed. So right now my turbo set-up is like real big cold air intake.

My issue is that until a few days ago my car cold started at an AFR of 13.6 now it cold starts at an AFR 14.4, and under full throttle my car used to sit at an AFR of 12.8-13.0 now it sits at 14.1. Could this change in AFR be due to a faulty O2 sensor or is it something else?

My bad on the confusion

theres no way to tell if the sensor is faulty unless you look at it with a scantool. i highly doubt the sensor is faulty. even though the turbo is not building boost it is still moving air into the engine. this maybe the cause of the full throttle lean out. what did you do to purposely not build boost?

turbo has an internal wastegate so i'm just holding the flapper open right now.

do u have an intercooler and a blow off valve?

What wide band kit do you have? What ecu do you have OBD1 or 2?

ya intercooler, BOV, the whole thing minus injectors and installed ecu. Just waiting on the ones i ordered to get here then get it tuned. I have an AEM UEGO wideband kit and just running the stock OBD2 ecu right now

Did you leave the narrow band number 1 o2 sensor or are you sending a happy signal to the ECU and remove O2#1? I do not know anything of the AEM sensor. I have a innovate lc1 that would send a happy signal to the ecu to keep the check engine light off and keep from altering too much fuel change when i was boosting with my obd2 ecu and an AFC Hack with no number 1 narrow o2 sensor.

And how is the wastegate, are you just driving around with a ginormous exhaust leak?

Its an internal wastegate that dumps into my exhaust so no exhaust leak. I have taken out the O2 sensor that was in the cat and removed the cat so there is just my AEM UEGO sensor and O2 sensor #1. But my AFR was standing where it should have been until a few days ago. I took it to the Honda dealer and got them to run codes on my car and it turned up nothing. he thinks it could be anyone of a number of sensors that have just worn out something and not readinbg right.

Well it sounds like your ecu is doing what it is supposed to be doing, its trying to keep 14.7 afr. Get rid of all that ECU and go obd1 when you really boost and move that wide band in the o2#1 bung. The honda dealer sounds like they don't want to mess with it and so they told you that and probably don't even know what the air fuel ratios should be outside of 14.7:1.

If you pulled the battery cables and did all that work to it, you reset everything in the ecu, pull the cables again and let them sit for a while, maybe it will go richer again, i wouldn't worry about it, pull the plugs and look for detonation if you are worried and make a set of detonation cans.

Ya i have an OBD1 ECU w/S300 installed in it. Why would i move the AEM O2 sensor in to the stock # O2 sensor location? doesn't the ecu still need that one to function regardless if it is OBD1 or OBD2

but ya it is odd, full throttle and cold start are both running to lean but under normal driving conditions everything is fine.

you arn't going to hurt anything with those numbers NA.

You need a narrow band O2 signal for obd2 honda ecu's only if you run that ecu but that can be tricked with a lc1 wideband. You don't need it for obd1 ecu's because you will run the wide band through the ecu so you can data log through the original narrow band circuit. You have to remove the check sum so you don't get check engine lights because of the new wide band. You will be tuning off of vacuum/boost (map sensor) and rpms. The wide band does not change the air fuel like a narrow band did orignally. You want the wide band close to the turbo for more accurate readings, the further back in teh exhaust stream you loose some accuracy especially if you have minute to large exhaust leaks. The o2 1 port is a good place.

DO i have to hook up the AEM wideband to the OBD1 ecu? i thought data logging was just optional?

No you don't have to but why wouldn't you? Datalogging is the fun part along with the tuning, i hook my computer all the time, that is how i have gotten 37-38 miles to the gallon per tank fill. I bet i would get 40 if i could keep my foot out of the pedal. This is in a 2000 civic si. I also datalog every trip down the drag strip so i can lean it out just a little more or add little bits of timing or back off if needed. But if thats not something you want then leave the wide band as a stand alone unit.

Ya i really have no idea on how to tune or mess around with one, so i think i will leave out the data logging part. Last thing i want to do is screw up my tune and detonate my engine.