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.

1987 Plymouth Horizon AutomaticFACTORY OEM SERVICE PROCEDURE

Spark Control Computer Spark Test

Warm engine to normal operating temperature. Set basic timing. Disconnect carburetor switch or unground it. Ensure coolant temperature sensor is connected and working properly.
Remove and plug vacuum hose at vacuum transducer. Connect a vacuum pump to the vacuum transducer and apply 16 in. Hg vacuum. Increase engine speed to 2000 RPM. Timing should be within 4° of specifications. See SPARK ADVANCE TEST SPECIFICATIONS table. If computer fails to obtain settings, replace computer.

SPARK ADVANCE TEST SPECIFICATIONS ⁽¹⁾

Application

Computer Part No.

⁽²⁾ Advance

Shelby

Fed.

5226449

38°

Calif.

5226645

36°

All Other Fed. & High Alt. Models

Man. Trans.

5226439

40°

Auto. Trans.

5226433

40°

All Other Calif. Models

Man. Trans.

5226455

40°

Auto. Trans.

5226451

36°

⁽¹⁾	Engine speed of 2000 RPM and 16 in. Hg vacuum applied.

⁽²⁾	All readings plus or minus 4°. If amount of advance differs from emission label, use label as accurate listing.

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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