2004 Dodge Neon P0304 Check Engine Light: Misfire Diagnosis and Fixes

The mileage on your vehicle and the brand of spark plugs and ignition wires you used are important. Are the connections secure? Misfires in 2004 Dodge Neons are typically straightforward issues. I've diagnosed hundreds of these cases at a dealership — proper diagnosis starts with checking basic components. Good luck, and please update us on your progress! Heff

I used Duralast ignition wires and Bosch spark plugs. The original plugs were pre-gapped, but I measured them at 0.041 inches — higher than the recommended 0.032 inches. I adjusted the gap manually. The car has 42,000 miles on it.

Using Bosch platinum spark plugs may not be ideal for a 2004 Dodge Neon — many users report that original Champion brand plugs perform better and are more reliable. Platinum plugs are especially sensitive to gap settings. I strongly recommend using the OEM or factory-recommended spark plug type, as specified on the emissions decal under the hood (or at the dealership if the decal is missing). The incorrect gap suggests you may have installed wrong parts. Aftermarket wires like Duralast can be a common cause of misfires. While they're often priced similarly to OEM options, some users report poor performance and early degradation. I've seen this issue repeatedly — especially in older Neons with high mileage. I'm not against aftermarket parts entirely, but for ignition systems, original equipment manufacturer (OEM) components are generally more reliable unless cost or availability is extreme. Many forum members have shared similar experiences. In most cases, 95% of P0304 misfire issues in Neons stem from spark plugs and wires — if no other engine or fuel system problems exist, replacing the correct OEM parts should resolve it. Most auto parts stores will offer refunds or exchanges for incorrect parts. The proper plug part number can be found on the emissions decal under the hood. If that's missing, your dealer can provide the correct specification. The gap issue is a strong indicator of wrong plugs — and platinum-type spark plugs are especially sensitive to improper gapping. I've personally experienced this multiple times in recent months. Best of luck — keep us posted! Jeff

Thanks for the advice, Jeff! I replaced the spark plugs with the correct OEM Champion brand as recommended. The check engine light went off initially, but it returned every time I stopped driving. Now, when I stop — whether at a red light or in traffic — the light flashes and the car begins to shake. What should I check next?

If the correct plugs and wires didn’t resolve it, your next steps should include: a compression test on cylinder 4, testing the coil pack output, swapping fuel injectors between cylinders (to isolate the issue), or switching the ignition wire for cylinder 4 with another that has proper reach. If the code remains P0304 after these tests, then the misfire is still present — and your vehicle is likely experiencing a mechanical issue. Make sure the diagnostic code hasn’t changed — if it did, that would point to a different cylinder or system. At this stage, you should rule out common variables like faulty coil packs or clogged injectors. I haven't personally tested Duralast wires, so I can't confirm their performance — but persistent misfires suggest an underlying issue beyond just the spark plug or wire. Keep us posted! Jeff

I have the same problem. My check engine light shows a misfire in cylinder 3. I have an extended warranty, so I'm planning to take it to a service center and see if they can identify the root cause. I'll update you once I get results.

I own a 1998 Dodge Sebring LXI and have experienced exactly what others are describing — misfires, engine shaking, and poor fuel economy (around 13–15 miles per gallon). I found that my distributor cap was cracked and the original ignition wires were arcing. After replacing both with a Well's cap and Duralast wires, the car started smoothly for about 10 minutes — but now it’s back to full misfire symptoms. Last night, I checked in the dark and saw arcing again on the wires. I can confirm that Duralast wires are likely causing the issue in my case. Even though there was no heat source near the wire looms, the arcing is clearly visible. I had been misdiagnosing this as a faulty ECT sensor (engine coolant temperature), but after replacing it twice with no improvement, I shifted focus to ignition components. I’m confident you’re experiencing the same symptoms and root cause — especially since I just replaced my wires with higher-quality ones. I’ll be swapping them out soon. Best of luck! I hope this helps — your fuel economy may suffer similarly. Jesse

We also have a 2004 Dodge Neon with the same P0304 issue. We've taken it to the dealership four times and spent nearly $1,000 — but no resolution has been found. Has anyone else successfully fixed this problem? If so, what was the actual cause?

If correct OEM spark plugs and wires did not resolve the issue, your next step should be to inspect the coil pack and fuel injector for cylinder 4. Carbon buildup on valves can also cause misfires. A full compression test — both static and while running — is essential to determine if there's a mechanical or internal engine problem.