1999 Dodge 3500 Ram Van P0305 Recurring Cylinder 5 Misfire - Diagnosis & Solutions

The 1999 Dodge 3500 Ram has a V6 engine — which specific configuration? Your mention of 'high quality components' raises a concern: if these were aftermarket and not OEM Dodge parts, they may not be optimal. Do you have an OBD2 scanner that shows all codes and live data? Is P0305 the only code present? Motorhomes often sit idle seasonally — does your vehicle follow this pattern? Start with a fuel pressure test. Then perform a KOEO (Key On, Engine Off) check to observe any pressure drop. Add a can of Techron or Seafoam fuel system cleaner and update us on results.

Thanks for the clarification. Only P0305 is present. The vehicle was inactive from 2008 to 2012 (88,000 miles), then became a daily driver in 2012. It now has 139,800 miles and averages about 50,000 miles annually. The P0305 code first appeared around 4 months ago at approximately 125,000 miles. I have an OBD2 scanner that detects only one code — P0305 — and supports live data reading. The engine is a 360 V6. I'm skeptical about aftermarket high-voltage components (like spark plugs) causing isolated cylinder #5 misfires, since P0305 specifically points to cylinder five. Is this code generic or specific? I recently completed a 7-day, 2,500-mile trip with no issues. The next day, the P0305 code returned. Thanks again, Pete

With your scanner, check the ECT (Engine Coolant Temperature) sensor — ensure it reads ambient temperature at startup and reaches operating temperature (~195°F). Review fuel trims (FTs), as they can reveal underlying issues. The freeze frame data may also provide valuable clues. Are all P0305 codes generic? Yes, technically all P0001–P0999 codes are labeled 'generic' because manufacturers use the same naming convention. However, P0305 is fairly specific — it indicates a misfire in cylinder #5. Did you replace both fuel injectors (#5 and #7)? I recommend starting with the data points I suggested (ECT, FTs, freeze frame) before suspecting a faulty injector or leak. A bad injector could be responsible, but only after confirming system-level data. Merry Christmas — enjoy the holidays! I’ll follow up when possible. Have a great holiday season.

Thanks for the advice. I replaced both cylinder #5 and #7 fuel injectors (adjacent on the rear left side of the engine) to rule out any issue with one or both. The problem is very intermittent — the engine can show P0305 twice in a day or go thousands of miles without an issue. The misfire always occurs before the code appears. I will perform a fuel pressure test next. This is my first time using an OBD2 scanner, so I’ll be doing some research and sharing updates soon. Thanks for your help, Pete

Confirmed: driver-side cylinders are #1, #3, #5, #7 from front to back. Add a recommended fuel system treatment (like Techron or Seafoam) to the tank. Let it sit over the holidays and use your scanner to learn how to interpret data. You suspect an intermittent issue but it's confined to cylinder #5 — injectors are often a common cause. When performing a fuel pressure test, always check for leak-down during KOEO (Key On, Engine Off) to ensure system integrity. This helps rule out fuel delivery issues.

KOEO — I understand that. What about ECT? Still reviewing the details. The confusing part is why only cylinder #5 is affected. I replaced both injectors (#5 and #7) a few days ago. After running for two hours (including 45 minutes of idle), the engine ran smoothly. Then, upon restarting, it immediately developed a misfire and triggered P0305 again. Why only cylinder #5? I understand leak-down can cause issues — that makes sense. But why specifically cylinder #5? Could fuel contamination be involved? Or is there a leak in the left bank fuel rail (which feeds cylinder #5)? Thanks, Pete

Possible causes I can think of: - Sticking valve in cylinder #5 - Distributor defect affecting only cylinder #5 - Wire harness fault leading to cylinder #5 injector - Faulty engine control module (ECM) - Hydraulic lifter failure - Clogged catalytic converter - Oxygen sensor malfunction (which could cause a weak cylinder to trigger P0305) All of these could result in a weak cylinder (#5) being detected and triggering the code. I'm asking this forum because I suspect others may have faced similar issues and found solutions. Thanks, Pete

I’m experiencing the same issue on a 2006 Jeep Commander — only cylinder #5 has misfires. I’ve already replaced the power coil, plug, and injector for that cylinder. I also swapped out the fuel injectors. I inspected rockers and valves — appear to be in good condition. I’m now considering mechanical causes. If it were an oxygen sensor issue, I’d expect multiple related codes rather than just P0305. I’ll perform a compression test next. Any other suggestions for diagnosing this specific misfire would be appreciated.