The ignition system, which includes everything from coils and coil packs to electronic ignitions and computers, can be a box of mysteries to many people. How can you determine whether a coil causes your car's issues? Checking the coil is the initial stage in diagnosing the system, and it will inform you whether or not the coil is working properly. The process is the same regardless of the kind of vehicle you drive; the only difference is the coil location and type.
Use a wrench to loosen the bolt on the negative battery wire, then place it somewhere where it won't come into contact with the battery while you're working.
On your vehicle, check for the coil. Disconnect any wires attached to the positive and negative terminals on the coil using a wrench, then disconnect the middle wire that runs from the coil to the distributor. These will be posts on the top of the coil on older-style coils. Newer systems that utilize coil packs need you to disconnect the wire harness connector and use the connector's pins as contact points.
Connect your ohmmeter's first test lead to the negative terminal and the other to the positive terminal. From the meter, measure the resistance across the terminals. You're searching for a resistance range of 0.70 to 1.7 ohms. Any variation from that range indicates a faulty coil.
One of the test leads should be moved from the side terminal to the coil's high-tension terminal in the middle. Since you measure resistance rather than amps or volts, it really doesn't important which lead connects to which terminal. Take note of the ohmmeter value; it should be between 7,500 and 11,000 ohms. Anything outside of that suggests a faulty coil.
Reconnect the coil wire to the high-tension connection and the remaining wires to the side terminals. Install and tighten the retaining nuts on the side terminals using a tool.
Tighten the clamp's bolt and reconnect the negative battery wire to the battery terminal.