1993 Geo Prizm Base, StandardFACTORY OEM SERVICE PROCEDURE

Ignition Timing

  1. Warm engine to normal operating temperature. Turn engine off. Remove cover from Data Link Connector (DLC), located on left strut tower. Connect a tachometer to battery and terminal No. 19/IG (Black wire) of DLC. See Fig 1 .
    CAUTION: DO NOT  ground terminal No. 19/IG in Data Link Connector (DLC). Grounding this terminal could result in ignitor or ignition coil damage.
  2. Start engine. Ensure all accessories are off. With transaxle in Neutral, ensure idle speed is 650-750 RPM. If idle speed is not as specified, see IDLE SPEED  under IDLE SPEED & MIXTURE.
  3. Turn engine off. Connect timing light to No. 1 spark plug wire. Install jumper wire between terminals No. 3/E1 (Brown wire) and No. 8/TE1 (Blue/White wire) of DLC. See Fig 1 .
  4. Start engine, and check timing mark alignment on crankshaft pulley with timing marks on timing belt cover. Notch on crankshaft pulley should line up at 10 degrees BTDC on timing indicator at each flash of timing light.
  5. If adjustment is required, loosen distributor hold-down bolts, and rotate distributor until a 10-degree BTDC reading is obtained. Tighten distributor hold-down bolts to 15 ft. lbs. (20 N.m). Recheck ignition timing.
  6. Turn engine off. Remove jumper wire from DLC. Recheck timing. Ignition timing should be varying between 5 degrees and 15 degrees BTDC. Remove timing light.
Fig 1: DLC Terminal ID
G93H78086Courtesy of GENERAL MOTORS CORP.
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.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.