Quote:
Originally Posted by crakrz
Fuel trims look weird. Have you replaced the o2 sensors. The voltages don’t seem to be switching enough.
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I think you've nailed it mate - this is from the NGK website...
"Using an appropriate connecting device, connect the sensor output to your oscilloscope; do not disconnect the sensor from the
ECU. Run the engine at approximately 2000 rpm. A properly functioning oxygen sensor will show a rapidly fluctuating output voltage between approximately 0.1 and 1.0 volts. The time taken for the voltage to change from 0.1 V to 1.0 V (referred to as the lean to rich response time) should be about 300 milliseconds. A similar time should be measured when the voltage changes from 1.0 V to 0.1 V (rich to lean response time).
If the sensor output is constant or the response time is too slow the sensor should be changed. It is a good idea to check the oxygen sensor function at every tune up and before submitting cars for emission tests. A slow sensor will affect fuel economy. A new sensor will pay for itself by cutting fuel costs."