Note. DO NOT attempt to adjust idle mixture and idle speed. Both are controlled by Electronic Control Module (ECM). Incorrect idle speeds are normally caused by dirty throttle plate or vacuum leaks. Ensure all vacuum components are functioning properly.
Note. Controlled idle speed and IAC count can be checked using scan tester. See CONTROLLED IDLE SPEED & IAC COUNT .
- Ensure no trouble code(s) are present, IAC system is okay, and ignition timing is correct. Block drive wheels. Apply parking brake. Connect Tech 1 scan tester to Data Link Connector (DLC). Put scan tester into OPEN mode.
- Start engine and bring to normal operating temperature. Check for correct state of Park/Neutral switch on scan tester. Check if idle speed and IAC valve pintle position (counts) are as specified. See «CONTROLLED IDLE SPEED & IAC COUNT»(ref-20048-S01403987142001010200000) .
- If idle speed is not within specification, refer to «TESTS W/O CODES - GASOLINE»(ref-20057) article in this section.
| Application | Idle RPM | (1) IAC Counts |
|---|
| CPI |
| "L" Series (A/T) (2) | 625 | 15-50 |
| "M", "S" & "T" Series (A/T) (2) | 550 | 5-40 |
| TBI |
| "C" & "K" Series |
| Auto. Trans. (2) (4) | 537 | 5-30 |
| Auto. Trans. (2) (4) | 650 | 20-35 |
| Man. Trans. (3) | 550 | 2-20 |
| "G" Series |
| Auto. Trans. (2) | 538 | 5-30 |
| Man. Trans. (3) | 650 | 5-30 |
| "L" Series |
| Auto. Trans. (2) | 625 | 5-50 |
| Man. Trans. (3) | 700 | 3-30 |
| "M" Series (A/T) (2) | 538 | 5-30 |
| "P" Series |
| Auto. Trans. (2) | 650 | 5-30 |
| Man. 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. |
| (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. |
CONTROLLED IDLE SPEED & IAC COUNT
