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P0303 Diagnostic and Fix for 1997 Chevrolet Lumina 3100 - Spark Plug, Injector, and Compression Issues

Model: 1997 Chevy Lumina 3100 Fault Code: P0303 Posted: 2006-09-05 11:03

I own a 1997 Chevrolet Lumina 3100 that started exhibiting a knocking noise while driving on the highway. Shortly after, the SES light began flashing, which later switched to steady but the knocking persisted. I took the vehicle to AutoZone and retrieved the OBD2 code, which reads P0303 — indicating a misfire in cylinder 3. After replacing the spark plugs and ignition wires with new Bosch Platinum plugs and Borg & Warner wires, the issue remained unresolved. The engine still produces a knocking sound, and I notice a gasoline-like odor from the exhaust, along with an unidentifiable secondary smell. I've reviewed OBD2 trouble code information at http://www.obd-codes.com/trouble_codes/p0303.php but am unsure of the next steps. I’ve tested the ignition coil visually and believe it is functioning properly (though I was shocked by the plug wires during testing, which may not be a reliable method). The issue could stem from fuel injection problems or low compression. To confirm, I plan to inspect the spark plug for fuel wetness, perform a visual spark test, and use a compression tester to evaluate cylinder performance. If either the injector resistance is inconsistent or compression is significantly low, I will need to take the car to a professional shop — as I currently don’t have the time or tools for advanced diagnostics. Any suggestions on troubleshooting P0303 specifically in this model would be greatly appreciated.

Related fault codes
P0303
Comments (3)
Anonymous 2006-09-05 13:00

Check the fuel injectors using a digital multimeter (DVOM) to ensure consistent resistance across all cylinders. Testing coil output by hand is unreliable — use proper tools for accurate readings.

Anonymous 2006-09-05 14:51

I installed Bosch Platinum spark plugs and Borg & Warner wires. I just realized today that I never checked if the spark plug was wet with fuel — a key indicator of injector function. I’ll pull the plug, ground it, and observe for spark. Then I'll run a compression test to check cylinder health. If either the injector or compression is faulty, I’ll have to take it to a shop — as I’m only a medium-level DIYer. Coils are relatively easy to diagnose and replace though.

Anonymous 2006-09-05 15:46

Try using OEM Delco spark plugs designed specifically for the 1997 Chevrolet Lumina — they’re often more reliable than aftermarket brands. I’ve seen this issue repeat in multiple threads: users install wrong plug types and get P0303 after a few days. It’s surprisingly common! How many miles does your car have? Has the intake manifold gasket been replaced yet? Let me know how it goes — good luck, and please update us on progress.