Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1994K 2500 SUBURBAN 4WD V8-350 5.7LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSADJUSTMENTS
1994 Chevrolet K 2500 Suburban 4WD V8-350 5.7L
Computers and Control Systems: Adjustments
1994 Chevrolet K 2500 Suburban 4WD V8-350 5.7LSECTION Adjustments
CONTROLLED IDLE SPEED CHECK:
NOTE: Before performing this check, there should be no codes displayed, idle air control system has been checked and the ignition timing is correct.
- Set parking brake and block drive wheels.
- Connect a SCAN tool to the DLC connector with tool in Open Mode.
- START engine and bring it to normal operating temperature.
NOTE Normal engine operating temperature range is 92° C to 104° C (196° F to 222° F)
- Check for correct state of PRNDL position (R-D-L) switch on SCAN tool.
- Check specifications chart for controlled idle speed and IAC valve pintle position (counts).
- If within specifications, the idle speed is being correctly controlled by the control module.
- If not within specifications, refer to DIAGNOSIS BY SYMPTOM / ROUGH, UNSTABLE OR INCORRECT IDLE.
MINIMUM IDLE AIR RATE CHECK
Minimum Idle Air Rate is not adjustable on this engine.
UNDER 8500 GVW
CONTROLLED IDLE SPEED
Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2]
Man. N 650 +/- 25 5-30 CL
Auto D 525 +/- 25 5-30 CL
[1] On manual transmission vehicles the scanner will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level.
[2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop).
OVER 8500 GVW
CONTROLLED IDLE SPEED
Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2]
Man. N 700 +/- 25 5-30 CL
Auto D 550 +/- 25 5-30 CL
[1] On manual transmission vehicles the scanner will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level.
[2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop).
NOTE: Before performing this check, there should be no codes displayed, idle air control system has been checked and the ignition timing is correct.
- Set parking brake and block drive wheels.
- Connect a SCAN tool to the DLC connector with tool in Open Mode.
- START engine and bring it to normal operating temperature.
NOTE Normal engine operating temperature range is 92° C to 104° C (196° F to 222° F)
- Check for correct state of PRNDL position (R-D-L) switch on SCAN tool.
- Check specifications chart for controlled idle speed and IAC valve pintle position (counts).
- If within specifications, the idle speed is being correctly controlled by the control module.
- If not within specifications, refer to DIAGNOSIS BY SYMPTOM / ROUGH, UNSTABLE OR INCORRECT IDLE.
MINIMUM IDLE AIR RATE CHECK
Minimum Idle Air Rate is not adjustable on this engine.
UNDER 8500 GVW
CONTROLLED IDLE SPEED
Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2]
Man. N 650 +/- 25 5-30 CL
Auto D 525 +/- 25 5-30 CL
[1] On manual transmission vehicles the scanner will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level.
[2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop).
OVER 8500 GVW
CONTROLLED IDLE SPEED
Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2]
Man. N 700 +/- 25 5-30 CL
Auto D 550 +/- 25 5-30 CL
[1] On manual transmission vehicles the scanner will display RDL in Neutral. Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level.
[2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop).
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.