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.
Run Mode
Once the engine starts and is operating normally, the timing will be controlled by the computer, based upon information received by the data sensors.
Spark timing and dwell cannot be adjusted in the run mode. If the computer fails, the system will go into the start mode. This enables the vehicle to be driven in for repair; but performance and fuel economy will be poor. If the start mode fails, the engine will not start or run.
The amount of spark advance is determined by engine speed and engine vacuum. Advance based upon engine vacuum is allowed by the computer when the carburetor switch is open. The amount of advance is programmed into the computer and is proportionate to the amount of vacuum and engine RPM. Advance based upon engine speed (RPM) is allowed by the computer when the carburetor switch is open and vacuum level is steady. This advance from speed is programmed into the computer, controlled by engine RPM, and will build at a slow rate. If carburetor switch closes, advance from speed will be cancelled.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.