Quote:
Originally Posted by nzporsche944s2
Intake leak on the lean side can cause this on some engines (e.g. Intake manifold gasket leak)
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Blamo. We have a winner. However, I will also add this: It could also be that the threshold for triggering lean has been exceeded by use of oxygenated fuel. Cars have a pretty wide threshold for lean readings due to sensor wear, and on a V8 one side may run 1-4 points leaner than the other.
If one side was marginal (close to threshold) but still ok before oxygenated fuel, then using oxygenated will push it over the edge.
My BMW did this crap, and by putting a new MAF in it brought the correction readings down on both banks far enough - prior to the new MAF one side was borderline OK, the other was occasionally tripping the lean code- since the readings are never stable, they hover within a range. The new MAF brought the corrections way down so both sides were well within limits.
Look at the actual correction values on a scanner while running, if one side is just popping over the limit on occasion and both values are otherwise a few points within each other I'd start checking a sensor before tearing into the manifold.
rjp