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.
1990 Chevrolet APVFACTORY OEM SERVICE PROCEDURE
All Models (Except Diesel)
- Set parking brake, block drive wheels and place transmission in Neutral or Park. Warm engine to normal operating temperature. Turn A/C off (if equipped). Ensure SERVICE ENGINE SOON light is off.
- Disconnect Tan/Black wire EST by-pass connector located behind electrical junction box cover or near distributor. DO NOT disconnect 4-wire connector at distributor.
- Connect timing light to No. 1 spark plug wire. Check timing and adjust if necessary. See V8 IGNITION TIMING SPECIFICATIONS table. Reconnect EST by-pass connector and clear ECM trouble code.
V8 IGNITION TIMING SPECIFICATIONS (Degrees BTDC @ RPM)
| Application | Man. Trans. | Auto. Trans. |
|---|---|---|
| 5.0L (VIN H) | 0 @ Idle | 0 @ Idle |
| 5.7L (VIN K) | 0 @ Idle | 0 @ Idle |
| 7.4L (VIN N) | 4 @ Idle | 4 @ Idle |
Factory Service Tools
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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.
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