System Too Rich

If air/fuel ratio is too rich, idle speed will be too low and "Scan" tester counts will usually be greater than 80. The system may be obviously rich, with Black smoke from the tailpipe. "Scan" tester and/or voltmeter will read an oxygen sensor voltage signal fixed greater than 800 mv (.8 volt). Look for high fuel pressure or injectors leaking or sticking. Remove IAC and inspect bore for foreign material or evidence of IAC valve dragging the bore.