1990 Isuzu Impulse AutomaticFACTORY OEM SERVICE PROCEDURE

Idle Speed & Ignition Timing

For adjustment procedures, see ADJUSTMENTS - EFI article.

IDLE SPEED SPECIFICATIONS

Application Idle RPM
Amigo & Pickup
2.3L (1)(2) 900
2.6L (1)(3)(4) 900
Impulse (1) 850
Trooper
2.6L (1)(3) 900
2.8L (1)(5) 800
(1) Transmission or transaxle in Park or Neutral.
(2) Disconnect and plug vacuum advance, canister purge and EGR vacuum lines.
(3) Disconnect fuel pressure regulator Vacuum Switching Valve (VSV). Disconnect and plug canister purge and EGR vacuum lines.
(4) On California models, disconnect and plug vacuum line for EGR vacuum switching valve.
(5) Disconnect distributor set timing connector. Connector is a Black/White wire with White connector, located below tray at rear of center console. If specification varies from underhood emission label, use specification from label.
IGNITION TIMING (Degrees BTDC @ RPM)

Application Base Timing
Amigo & Pickup
2.3L 6 @ 900
2.6L 12 @ 900
Impulse (1) 9-11
Trooper
2.6L 12 @ 900
2.8L 10 @ 800
(1) With jumper wire installed in ALDL diagnostic connector, located behind right side of instrument panel. Increase engine speed to 1500-2000 RPM to read timing specification (if necessary).
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

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.