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HOMESERVICE MANUALSGMC1986SUBURBAN C2500, 5.7 M, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCEADJUSTMENTTUNE-UP - V6ADJUSTMENTSIGNITION TIMINGALL CALIFORNIA & 2.8L FEDERAL MODELS
1986 GMC Suburban C2500, 5.7 M, Standard

All California & 2.8L Federal Models

1986 GMC Suburban C2500, 5.7 M, StandardSECTION All California & 2.8L Federal Models
  1. Install timing light with an adapter between No. 1 spark plug and No. 1 spark plug wire or use an inductive pick-up. Do not puncture wire. Disconnect 1-wire connector at distributor. DO NOT disconnect 4-wire connector at distributor.
  2. Check and adjust ignition timing with engine at normal operating temperature and transmission in Park or Neutral. Reconnect 1-wire connector at distributor. Clear trouble code by removing ECM power fuse for 10 seconds.
IGNITION TIMING SPECIFICATIONS (DEGREES BTDC @ RPM)

Application Man. Trans. Auto. Trans.
2.8L (1) 10 @ (2) (2) 10
4.3L Carb.
Federal 0 @ 600 0 @ 500
Calif. & Hi. Alt. 4 @ 600 4 @ 500
4.3L TBI (1) 0 @ (2) (2) 0
(1) Idle speed on TBI models is not adjustable.
(2) At idle speed.
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.