Here's a general guide, but you should consult a repair manual specific to your Blazer's year and engine for precise locations and potential variations:
1. Identify the Coil:
* Location: The coil is usually located near the distributor (if your Blazer has one - some models had electronic ignition without a distributor cap) or on the engine block, often near the spark plug wires. Consult your repair manual for the exact location.
2. Gather Tools:
* Socket wrench (likely 7/16" or ½" depending on the coil mounting bolt size)
* Ratchet
* Extension (may be needed depending on coil location)
* Wire brush (to clean terminals)
* New ignition coil (make sure you get the correct one for your engine)
* Gloves (optional, but recommended)
3. Disconnect the Coil:
* Spark Plug Wires: Carefully disconnect the spark plug wires from the coil tower. Make a note of which wire goes to which cylinder (or take a picture) to avoid misfiring after reconnection.
* Electrical Connectors: There will be one or more electrical connectors attached to the coil. Unplug these carefully.
4. Remove the Coil:
* Bolts: The coil is usually held in place with one or two bolts. Loosen and remove these bolts using your socket wrench and ratchet.
* Remove the Coil: Carefully remove the coil from its mounting location.
5. Install the New Coil:
* Clean the Mounting Surface: Clean any dirt or corrosion from the mounting surface on the engine block or distributor.
* Install the Coil: Align the new coil and install it in the same position as the old one.
* Secure the Coil: Tighten the mounting bolts securely.
* Reconnect the Electrical Connectors: Carefully reconnect the electrical connectors to the new coil.
* Reconnect Spark Plug Wires: Reconnect the spark plug wires to the new coil, ensuring each wire is connected to the correct cylinder.
6. Reconnect the Battery:
Reconnect the negative battery terminal.
7. Test the Ignition System:
Start your Blazer and check for proper ignition and engine performance. If there are still problems, double-check your connections and consult a repair manual or mechanic.
Important Considerations:
* Distributorless Ignition Systems (DIS): Some 1990 Blazers might have a DIS system. In this case, the coil may be integrated differently, and the process for replacement might vary. Refer to a repair manual specific to your vehicle.
* Repair Manual: This is crucial! A repair manual specific to your 1990 Chevy Blazer's engine will provide detailed diagrams, torque specifications, and troubleshooting steps. This guide is a general overview and might not apply perfectly to your specific vehicle.
* Safety: Always disconnect the negative battery terminal before working on the ignition system. High voltage can be dangerous.
If you are uncomfortable performing this repair yourself, it's always best to take your Blazer to a qualified mechanic. Improper installation can damage the ignition system or even lead to engine damage.
