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 MANUALSCHEVROLET1993FORWARD CONTROL 7.4 NREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - V8SUMMARYCODE 35, IDLE SPEED ERROR
1993 Chevrolet Forward Control 7.4 N
Code 35, Idle Speed Error
1993 Chevrolet Forward Control 7.4 NSECTION Code 35, Idle Speed Error
Code 35 will set when closed throttle engine speed is 150 RPM greater or less than correct idle speed for 20 seconds.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- IAC driver is used to extend and retract IAC valve. Movement is verified by changing engine speed. If no engine speed change occurs, valve can be retested when removed from throttle body.
- Checks IAC movement quality from step 1). Between 700-1500 RPM, engine speed should change smoothly with each tester light flash while extending or retracting. If IAC valve is retracted beyond control range (about 1500 RPM), it may take many flashes in extend position before engine speed reduces. This is normal on some engines. Fully extending IAC may cause engine to stall. This may be normal.
- Steps 1) and 2) verified proper IAC valve operation. This step checks IAC circuits. Each light on node light should flash Red and Green, while IAC valve is cycled. While color sequence is not important, if either light is off or does not flash Red and Green, check circuits beginning with poor terminal contacts.
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.