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Idle Speed & Mixture

NOTE: Idle mixture on fuel injected models is controlled by Electronic Control Module (ECM) and is not adjustable. Controlled idle speed and IAC count can be checked using scan tester. See CONTROLLED IDLE SPEED & IAC COUNT  table.
CONTROLLED IDLE SPEED & IAC COUNT

Application Idle RPM (1) IAC Counts
4.3L CPI
"L" Series
Auto. Trans. (2) 625 15-50
"M", "S" & "T" Series
Auto. Trans. (2) 550 5-40
4.3L TBI
"C" & "K" Series
Auto. Trans. (2)(4) 537 5-30
Auto. Trans. (2)(4) 650 20-35
Manual Trans. (3) 550 2-20
"G" Series
Auto. Trans. (2) 538 5-30
Manual Trans. (3) 650 5-30
"L" Series
Auto. Trans. (2) 625 5-50
Manual Trans. (3) 700 3-30
"M" Series
Auto. Trans. (2) 538 5-30
"P" Series
Auto. Trans. (2) 650 5-30
Manual Trans. (2) 700 5-30
"S" & "T" Series
Auto. Trans. (2) 650 5-30
Manual Trans.
Pickup 725 3-30
Utility 700 5-30
(1) Add 2 counts for engines with less than 500 miles. On 4.3L engines, add 2 counts for every 1000 ft. above sea level.
(2) Automatic transmission in Drive.
(3) Manual transmission in Neutral. Tech 1 scan tester will display "RDL" with transmission in Neutral.
(4) Calibration identification is not given by manufacturer. IAC count and actual RPM should correspond to one of these calibrations.
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