What’s A P0304 Code on a 2006 Ford Five Hundred

QuestionsCategory: Ask An ExpertWhat’s A P0304 Code on a 2006 Ford Five Hundred
Linda Thompson asked 4 months ago
Hi, I'm in need of some guidance with my 2006 Ford Five Hundred. Lately, when I'm idling, stopped at a light, or sometimes accelerating, my car experiences jerking and shaking. A few weeks ago, my engine light turned on, so I had it checked at O'Reilly, where I was advised that my spark plugs needed replacement. After spending $150 on new spark plugs, the problem persisted. Returning to O'Reilly, a different staff member informed me the issue was a P0304 code, indicating a misfire in cylinder 4. I'm hesitant to spend more on repairs without knowing the exact problem. Can you help me diagnose this correctly?
1 Answers
Zack Norman Staff answered 4 months ago
Hi there, Linda! You're right on the money with that P0304 code on your 2006 Ford Five Hundred, but let's break it down even further to help you out with diagnosing and fixing it:
  1. Understanding the P0304 Code: This code specifically indicates a misfire in cylinder 4. Misfires can be caused by various issues including faulty spark plugs, ignition coils, fuel injectors, or even internal engine problems.
  2. Diagnosing the Issue:
    • Swap Components: Since you've already replaced the spark plugs, consider swapping the ignition coil from cylinder 4 with another cylinder (like cylinder 2). If the misfire code changes to the new cylinder, the coil is likely at fault.
    • Check Compression: Perform a cylinder compression test. If the compression is low, a cylinder leak-down test can pinpoint whether the issue is with the valves, head gasket, or piston rings.
  3. Further Steps:
    • Vacuum Leak Test: Use carb spray or brake cleaner to spray around the intake manifold and fuel injectors while the engine is running. An increase in RPMs could indicate a vacuum leak.
    • Throttle Body Check: Given the model of your car, a dirty throttle body could also be a culprit. Be cautious with the coolant lines if you decide to clean it.
  4. Professional Diagnosis: If these steps don't reveal the problem, it might be time to consult a professional mechanic for a thorough diagnosis.
  5. Note on Repairs: It's understandable to feel frustrated about the cost of the spark plug replacement. However, regular maintenance like this can sometimes prevent other issues.
I hope these steps guide you towards resolving the misfire issue. Best of luck, and drive safely! Zack - Motor Verso Mechanics Team