To inspect the ignition coil when the engine is cold, begin by disconnecting the cable from the negative battery terminal. Look around the coil tower for carbon tracking, which appears as fine pencil-drawn lines, indicating an electrical shorting condition. If any carbon tracking is found, replace the coil and check the secondary wiring for excessive resistance. For 1986 through 1995 models, follow the primary wiring harness to the electrical connector and unplug it. If the connector is not easily accessible, detach the wires at the coil terminals. Disconnect the high-tension lead from the coil tower. Using an ohmmeter, measure the resistance across the primary terminals and compare it to the specified range in the Chapter's Specifications. Next, measure the secondary resistance by inserting a pointed metal tool into the coil tower, attaching one ohmmeter lead to it, and the other lead to the positive primary terminal. Compare the measurement to the coil secondary resistance in the Specifications, replacing the coil if it's out of range. For 1996 through 1998 models, unplug the electrical connector from the distributor and measure the primary resistance by touching the ohmmeter leads to the upper two terminals on the distributor side of the connector. Compare the measurement to the specified range. To check the secondary resistance, remove the distributor cap and touch one ohmmeter lead to the upper terminal and the other to the high-tension tower. Compare the measurement to the coil secondary resistance in the Specifications, and if it's outside the range, replace the distributor. For 1999 and later models, there are no primary and secondary resistance specifications provided by the manufacturer. The prescribed method by the manufacturer is to substitute a known good coil for a suspected defective one, but this approach is not recommended since electrical components cannot be returned. If the ignition system is malfunctioning after checking other components, it's advisable to have the coils checked out by a dealer service department. For replacement, on 1986 through 1995 models, disconnect the negative battery cable and label and disconnect the primary wires from the coil. Remove the high-tension lead from the coil tower. Remove the coil bracket-to-firewall screws and detach the coil. To install the new coil, reverse the removal procedure. If the new coil doesn't come with a bracket, slide the old bracket off the coil and secure the new coil into the bracket. Mount the coil on the firewall, ensuring the condenser, if equipped, is placed under the upper mounting screw. For 1996 through 1998 models, replace the entire distributor since the ignition coil is an integral part of it and cannot be replaced separately. For 1999 and later models, unplug the electrical connector from the coil and remove the coil retaining bolt, then pull the coil straight up to remove it. Installation is the reverse of removal.
Posted by GMPartsGiant Specialist 
