help on 02 sensor readings..
Thread Starter
On The Tree
Joined: May 2006
Posts: 104
Likes: 0
help on 02 sensor readings.. right i think im finally getting to the bottom of my part throttle misfire and over fueling...
i noticed while looking at the 02 sensors that bank 2's 02 sensor voltage was at about 600 ish and not changing as it should while bank one was happy at 300 ish jumping up and down nicely also bank 2 fuel trim was - 20 odd and and sometimes going up in seconds to -30 ! bank 1 was at 0 , also when i raise the throttle i can get the car to misfire i then put it into closed loop and it runs fine??
am i right in thinking that the ecu is getting a dodgy signal from the 02 sensor and banging loads of fuel in causing my misfire?
i noticed while looking at the 02 sensors that bank 2's 02 sensor voltage was at about 600 ish and not changing as it should while bank one was happy at 300 ish jumping up and down nicely also bank 2 fuel trim was - 20 odd and and sometimes going up in seconds to -30 ! bank 1 was at 0 , also when i raise the throttle i can get the car to misfire i then put it into closed loop and it runs fine??
am i right in thinking that the ecu is getting a dodgy signal from the 02 sensor and banging loads of fuel in causing my misfire?
FormerVendor
Joined: May 2006
Posts: 187
Likes: 0
Could be. Easiest thing to do is swap the two sensors from side-to-side. If the problem moves, then agreed it is your sensor. If the problem doesn't move, then you have something else going on.
Higher voltages on the O2 readings do indicate a richer AFR, and thus would reflect negative fuel trims as the PCM would want to pull fuel to achieve a stoich AFR. Stoich AFR is around 450mV, and the PCM expects swings of +/- 150mV (300mV to 600mV) to regularly occur.
Higher voltages on the O2 readings do indicate a richer AFR, and thus would reflect negative fuel trims as the PCM would want to pull fuel to achieve a stoich AFR. Stoich AFR is around 450mV, and the PCM expects swings of +/- 150mV (300mV to 600mV) to regularly occur.
When the PCM faults an O2 sensor it will force the
voltage to about 450mV. To see it stuck at 600mV
is a bit strange, that would appear to be a rich
output and drive negative trimming (possibly
leaning things out to the point of misfire or worse).
Simply unplugging the sensor ought to produce
the 450mV and a few codes, and force open loop.
If the forced voltage remains 600mV then maybe
there is a wiring or internal PCM fault. A steady
600mV would be very unlikely in open loop from
gas chemistry.
voltage to about 450mV. To see it stuck at 600mV
is a bit strange, that would appear to be a rich
output and drive negative trimming (possibly
leaning things out to the point of misfire or worse).
Simply unplugging the sensor ought to produce
the 450mV and a few codes, and force open loop.
If the forced voltage remains 600mV then maybe
there is a wiring or internal PCM fault. A steady
600mV would be very unlikely in open loop from
gas chemistry.
could be its telling the truth. has it set a P0175 code?
a stuck injector or one that found a new source of ground could cause
a problem like yours. does it do this on a cold start the misfire?
if not unplug the o2s as jimmy said and watch the trims as you disconnect
the right bank injectors one at a time.
a stuck injector or one that found a new source of ground could cause
a problem like yours. does it do this on a cold start the misfire?
if not unplug the o2s as jimmy said and watch the trims as you disconnect
the right bank injectors one at a time.
Thread Starter
On The Tree
Joined: May 2006
Posts: 104
Likes: 0
could be its telling the truth. has it set a P0175 code?
a stuck injector or one that found a new source of ground could cause
a problem like yours. does it do this on a cold start the misfire?
if not unplug the o2s as jimmy said and watch the trims as you disconnect
the right bank injectors one at a time.
a stuck injector or one that found a new source of ground could cause
a problem like yours. does it do this on a cold start the misfire?
if not unplug the o2s as jimmy said and watch the trims as you disconnect
the right bank injectors one at a time.
Last edited by Ricky_GD; Dec 22, 2008 at 01:54 PM.
whoooo 
