You need to be able to read data real-time like the pedal and throttle positions.

When my idle was horrible it was from a giant vacuum leak. Car set a code for ICV.

When wife's car acted similarly, it ingested the o-ring from the MAF into the throttle body and jammed the throttle plate.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)