Dave Hill
It is worth scoping the Oxygen Sensor VS the Mass Air meter during a snap wide open throttle event & observing the relationships.
Just today I had an Almira dropped off from my local Vauxhall Dealership. I had scanned it last week & pulled a P0171 & advised them to check the MAF sensor. They took my words too literally & replaced it & the light came back on.
Like I said, it returned today & again it had P0171 stored. The O2 vs MAF sensor snap throttle waveform exposed an immediate problem. The O2 sensor volts took a shift far into the negative volts. However there was no evidence of a fault during the idle & fast checks.
You really need to study the signals whilst challenging the components!
Darren Cotton has recently posted (on ilexa) a real nice example of this type of waveform. If we are lucky, he might post it on UKAT too...
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Nissan Micra K11 1.0 2002 - MIL on, weak mixture? (waveforms) - Fixed # - Malcolm Tripp March 16, 2011, 9:07 pm
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