Q:STFT LTFT Lean/Rich Condition
03-04-2007, 04:27 PM
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Q:STFT LTFT Lean/Rich Condition Quick question about lean/rich Fuel Trim conditions (using HPT):
When the STFT and LTFT being to read in the (+) values I know it represents a Lean condition and when in the (-) it shows a rich condition. My question is when it reads Lean does that actually mean that the O2 sensors is reading more O2 and less fuel or the opposite?
I thought I read, that when the Fuel trims are lean it actually means that atomization did not fully occur at the proper air/fuel mixture. Therefore, even though the fuel did not fully combust, which I would think reads rich at the O2s, actually reads lean.
When the STFT and LTFT being to read in the (+) values I know it represents a Lean condition and when in the (-) it shows a rich condition. My question is when it reads Lean does that actually mean that the O2 sensors is reading more O2 and less fuel or the opposite?
I thought I read, that when the Fuel trims are lean it actually means that atomization did not fully occur at the proper air/fuel mixture. Therefore, even though the fuel did not fully combust, which I would think reads rich at the O2s, actually reads lean.
03-04-2007, 04:34 PM
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O2 sensors work off residual exhaust oxygen. If you had incomplete
combustion you could have excess. But I wouldn't go pinning it on
that, without some other reason. I think except for an injector
problem atomization is pretty good, between spray cone and hot
intake valve. There seem to be more ways to get lean error than
rich, and poor atomization would need one specific problem to see.
combustion you could have excess. But I wouldn't go pinning it on
that, without some other reason. I think except for an injector
problem atomization is pretty good, between spray cone and hot
intake valve. There seem to be more ways to get lean error than
rich, and poor atomization would need one specific problem to see.
03-04-2007, 04:43 PM
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So since the sensors read off of left over O2 and if there is too much left (+0.45 i think) is that a lean or rich condition? I am voting lean...
03-04-2007, 10:26 PM
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Yes, if it's trimming positive (fuel) it means the PCM thinks
exhaust gas is lean (excess oxygen). Note that the PCM is
only as clued in as the sensors make it, sensors can be
fooled or fouled. Presuming the sensors are working right
you are carrying a slight lean error in whichever cell you're
talking about, which is being compensated.
exhaust gas is lean (excess oxygen). Note that the PCM is
only as clued in as the sensors make it, sensors can be
fooled or fouled. Presuming the sensors are working right
you are carrying a slight lean error in whichever cell you're
talking about, which is being compensated.
