Because a engine that is running with valve timing at "B" when the engine thinks it is at "A" can result in AFR errors. Especially if it is happening only at certain RPM ranges or types of driving.



So a motor may run fine at idle, and may run fine at WOT...but at transition in may be lagging, resulting in AFR errors. SO that these begin to show up over time, as a lean or rich conditions.


Is your motor running lean Or is it running rich, the DME has reduced the AFR as much as it can and is now saying 'its too lean'??? FIgure that out first.


Running a VANOS test on a computer is pretty simple. Obviously you need the tool....