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 MANUALSCHEVROLET1990CHEVY VAN G20, 5.0 H, 475/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/O CODESHESITATION, SAG OR STUMBLESYMPTOM DEFINITION
1990 Chevrolet Chevy Van G20, 5.0 H, 475/M40
Symptom Definition
1990 Chevrolet Chevy Van G20, 5.0 H, 475/M40SECTION Symptom Definition
Momentary lack of response when accelerator is pushed down. Can occur at any vehicle speed. Usually occurs when taking off from a stop.
Possible Cause & Correction Check the following:
- Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label.
- Check ignition wires for cracking, hardness and proper connections at both distributor cap and spark plugs.
- Check wires for pinches, cuts, and proper connections.
- Ensure fuel pressure is correct in all speed ranges. Also check for poor fuel quality or water contaminated fuel.
- Check for fouled spark plugs.
- Ensure correct PROM is installed in vehicle. Check with dealer for latest application information.
- Check for a binding or sticking TPS.
- Ensure initial ignition timing is properly set.
- Ensure ECM controlled idle speed is correct.
- Check EGR system for proper operation.
- Disconnect fuel injector electrical connectors. Crank engine and check for injector leaks.
- Check for an open in HEI ground circuit.
- Check canister purge system for proper operation.
- Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
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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.