At 04:48 PM 12/22/2011, John Lauterbach wrote: >Here are the results from voltage test. > >Voltmeter +-lead connected to lead from O2-sensor, -lead on bumper. >Engine not run for three hours and O2-sensor not connected to lead to >ECU > >0 volts from 0 to 120 seconds Cold sensor, not running yet.
>0.13 volts at 150 seconds Lean (could be any degree of lean)
>0.53 volts at 180 seconds Very close to stoichiometric
>0.30 volts at 210 seconds *Very* slightly lean
>engine stalls out at 240 seconds Unknown complication but needs chasing.
>connected O2-sensor to lead to ECU > >restarted engine > >0.45 to 0.55 volts ECU is biasing the sensor while sensor warms up.
>0.6 to 0.8 volts after engine at temperature and engine at about 2000 >rpm ECU has gone into closed-loop operation. Depending on meter, probably cycling fast enough that you're seeing an average reading, which suggests normalish operation. The suggestion is that it might be biased a bit rich, since .8 volts indicates some unknown rich condition.
>0.4 to 0.7 volts with rapid change within that range with engine at idle Within the limitations of the meter this is a normal reading. At idle the ECU lean-rich-lean cycle is a few seconds long (you can probably hear the engine note change slightly). Typical digital meters average their readings over a period of 1/3 to 1/2 second, so they can't meaningfully track the transitions. Again within the limits of the meter this looks like normal operation of the closed-loop system. The little gadget that Ken Lewis sells is based on an LM3914 chip and will give you better data since it responds instantly, and if you can get hold of an oscilloscope that will show exactly what's going on with the sensor. Typically an engine (at least a simple marine engine) that's too lean will cough when it tries to accelerate, rather than simply bogging. I'm guessing that your trouble is actually too rich. If you have an air leak into the exhaust or if one cylinder isn't firing properly the sensor will see a lean condition where none exists and the ECU will force the mixture rich, sometimes extremely rich. This could foul plugs at idle I think, as well as rubbishing your mileage. Yours, David |
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