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 MANUALSGMC1989VALUE VAN P3500, 3.9 L, AUTOMATIC, 475/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISCCC TESTS W/O CODESSURGES &/OR CHUGGLEPOSSIBLE CAUSE & CORRECTION
1989 GMC Value Van P3500, 3.9 L, Automatic, 475/M40
Possible Cause & Correction
1989 GMC Value Van P3500, 3.9 L, Automatic, 475/M40SECTION Possible Cause & Correction
Using a "SCAN" tool, ensure vehicle speed matches VSS reading. If tool is not available, or if readings do not agree, check:
- Intermittent EGR operation during idle condition. See EGR SYSTEM CHECK chart in the TBI TESTS/CODES article in this section.
- Ignition timing.
- In-line fuel filter for obstruction.
- Fuel pressure. See CHART A6 - FUEL SYSTEM PRESSURE TEST chart in the TBI TESTS/CODES article in this section.
- Alternator output. Repair if less than 9 volts or more than 16 volts.
- TCC operation. See TORQUE CONVERTER CLUTCH chart in the TBI TESTS/CODES article in this section.
- Inspect oxygen sensor for silicon contamination from fuel, or use of improper RTV sealant (sensor will have White, powdery coating that will result in high, but false, signal voltage). In return, the ECM will reduce amount of fuel delivered, causing a severe driveability problem.
- Remove spark plugs and check for cracks, wear, improper gap, burned electrodes, or heavy deposits. Check condition of distributor cap, rotor, and plug wires.
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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.