Joel, the pot has virtually nothing to do with the steady-state mixture. It simply signals when enrichment is necessary by delivering fast rate-of-change information to the ECU. I.e., acceleration enrichment. Poor contact fools the ECU into believing there is a rapid fluctuation in airflow, and it then falsely dithers the EHA, screwing up the idle.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7