2000 Buick LeSabre P0301 Misfire: Diagnosing Ignition System Issues with Limited Budget
I've replaced the #1 spark plug with a GM OE iridium spark plug, swapped out the #1 ignition wire with a new Delco wire (purchased directly from a Chevrolet dealer), and installed a new aftermarket Duralast coil in place of the original 1/4 coil. Despite these changes, the vehicle continues to misfire severely. Replacing the ignition wire actually worsened the condition, while the new coil improved it slightly—suggesting that the issue may not be isolated to cylinder #1. The car has nearly 70,000 miles on it, and all other spark plugs, wires, and coils remain original for now. Given this, I'm confused: if the misfire is originating from another cylinder, why does the OBD2 diagnostic code still show P0301 (indicating a misfire in cylinder #1)? I’ve conducted online research on common 2000 Buick LeSabre P0301 issues and remain uncertain about the next steps. While I recognize that professional diagnosis might be the most reliable solution, I’m hesitant to spend $100–$200 US to confirm a potentially simple part failure—especially since I don’t own an ohmmeter or OBD2 scanner (I can visit Auto Zone for code reading). An additional note: about a month ago, a piece of a Hefty trash bag became lodged under the exhaust manifold and pulled off the catalytic converter. The smell is now strong and unpleasant. Before my roommate and I drove it, the car had been used very little. She claims she can feel the misfire beneath the seat—approximately where the catalytic converter is located—and I experienced this sensation before replacing the coil. Given my tight budget and limited tools, what should I prioritize next? Is there a cost-effective troubleshooting path for P0301 on a 2000 Buick LeSabre? Or should I consider professional diagnosis despite the expense? Thanks in advance!
The P0301 code could still point to issues beyond just cylinder #1. Common causes include a faulty ignition module (which the coil mounts to), poor wiring connections, or a malfunctioning fuel injector. Replacing only one spark plug and wire in an ignition system is ineffective—either perform full ignition component replacement or seek professional diagnosis. Ultimately, you’ll need to commit to either a more extensive 'shotgun' approach with multiple parts or professional evaluation. Neither option is free.