ECM Strategy for Fuel and Spark Control

Troubleshooting driveability problems can be complicated, especially when there is so much diagnostic data available. You may sometimes find it difficult to decide which information is important and which information you should ignore. The key is getting back to the basics. That means the basic theory and the basic data.

As you have learned, fuel and spark calculation are, for the most part, affected by only a few input sensors. In fact, basic injection and spark calculation are a function of just two sensors; the engine speed and engine load sensors.

There are only four other sensors which have significant effects on injection (and to a lesser degree on spark advance corrections); those are engine coolant temperature, intake air temperature, throttle angle, and oxygen sensor feedback.

Data analysis is much easier once you are familiar with these six input parameters, their units of display, and their nominal values.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

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