nanayaw6

Check for an exhaust leak upstream of the O2 sensors. Also, you could always pull the negative battery terminal in the trunk for about 10 minutes to reset things.

E55amgsd

Will see bro thanks tho

kponti

Yes they can, however if you keep getting the same voltage map after map then no they cannot.

I will start with replacing the upstream O2 sensors if they are old enough, its peculiarly stuck at 0.9 volts. Should cycle a lil more than that.

nanayaw6

And I hope it's an easy fix for you as well. When I had this behavior, my O2 sensors only had around 5k on them so I ruled that out. Chased my tail until I decided to check for exhaust leaks and discovered the bolt holding the cylinder 8 header primary had backed out a little causing a leak right at the head. Fixed that then pulled the negative battery cable to reset the fuel trims and my AF was right back where it should.
Of course all this is based on your intake temps being normal etc.

Hulk

Also, try to only use 2 parameters in the logging since the obd slows down considerably with all those parameters. Try iat and timing only first and see how that goes

kponti

Talking about exhaust leaks, what is your fuel trims at idle and throttle on?

Nanayaw, if he had an exhaust leak upstream to the O2 sensor, wont his O2 voltage read more normal? By that I'm asking, won't the car "think" its running a normal AFR when its actually dumping fuel? Obviously I am curious cos you have had this happen to you

His O2 voltage seems rather rich. I am thinking his fuel trims will tell a lot more than anything else if he has an exhaust leak.

nanayaw6

Its tough for me to say what the car's O2 sensors would be doing in that scenario and also dependent on how bad of a leak we're talking. I have a wideband in my car which I monitor more. In my particular scenario, I was leaking right at one of the manifolds and I am running long tubes. For the periods where the other cylinders are firing, i'm sucking in air from the leak point down into the collector (still pre O2). In this case, the car reads a leaner O2 and starts to compensate by dumping fuel. Looking at his log I saw though, his O2 was at 0.9V. 0.9 x 14.7 gives 13.2 which is pretty lean if you ask me. But his dynos are showing the car to be running richer. Also, remember the resolution of our car's O2 sensors read via OBD is not that great. Like hulk mentioned, I would log IAt and timing for starters. Then log your pre-cat O2 sensors to make sure their readings are alternating between 1v and 0 as the motor is running.
Again, all this is assuming his O2 sensors haven't crapped out too you know. If he has anywhere near 100k miles, personally I would replace the pre cat 02 sensors and see if it affects things. Especially for a car I'm modding.

E55amgsd

Ok So I have no cats at all and my O2 sensors are just connected to the headers (down pipes ).I also have a check engine light that reads bank one and bank two catalytic something can't remember.told eurocharged about it and they said that doesn't matter .i believe that tuners tune this check engine light out so it won't appear..

Hulk

Ya the cel is for your rear O2 sensors, they can turn that off or you can turn them off with star, makes no diff