* Wires connected to the wrong spark plug: This is the most likely problem. The firing order for your engine is crucial. If even one wire is on the wrong plug, the engine won't fire correctly. Double-check the firing order in your owner's manual or a reliable online source (like a repair manual website for your specific Impala). Make absolutely sure each wire is connected to its proper spark plug.
* Wires damaged during installation: Did you accidentally nick or fray any of the wires during installation? A damaged wire can cause a poor connection or a short circuit, preventing the spark. Carefully inspect each wire for any damage.
* Loose or improperly seated spark plug wires: Ensure each wire is firmly seated on both the spark plug and the distributor cap (or coil pack if your Impala uses coil packs). A loose connection will prevent a good spark. Pay close attention to the clips that secure the wires – they need to snap firmly into place.
* Distributor cap issues (if applicable): If your Impala has a distributor, check the distributor cap for cracks or damage. Also, make sure the rotor is properly aligned and spins freely. A problem with the distributor cap can interfere with the spark delivery even if the wires are correctly installed.
* Damaged spark plugs: While you're at it, inspect the spark plugs themselves. They might have been damaged during the wire replacement, or they might have been worn out before you started. If they look excessively worn or damaged, replace them.
Troubleshooting Steps:
1. Verify Firing Order: This is the *most important* step. Get the correct firing order and meticulously check each wire.
2. Inspect Wires for Damage: Look for any nicks, cuts, or fraying on the wires.
3. Check for Secure Connections: Make absolutely sure every wire is firmly and correctly connected.
4. Inspect Distributor Cap (if applicable): If your Impala has a distributor, carefully examine it for any cracks, damage, or misalignment.
5. Check the Spark Plugs: Examine the spark plugs for wear and tear.
6. Try Starting Again: After making any corrections, attempt to start the vehicle again.
If you've checked all these points and the car still won't start, you might need further diagnostics. Consider seeking help from a qualified mechanic. Incorrectly installed spark plug wires can cause damage to your engine if the car is repeatedly cranked over unsuccessfully.
