Documenting a persistent diagnostic challenge on a 2014 Fleetwood Bounder 35K with Ford V10 engine at 49,000 miles. Experiencing random misfire codes exclusively at high RPMs (4000-5000) during hill climbs under load conditions. Check engine light flashes intermittently, occasionally solid.
Completed diagnostics include: full spark plug replacement, compression testing (all cylinders within spec), three ignition coils replaced, MAF sensor cleaning, premium fuel upgrade to 91 octane, and Lucas fuel treatment. Engine exhibits smooth idle and normal operation at standard RPMs. Scanner consistently returns P0300 random misfire code only during high-load, high-RPM scenarios.
Given the intermittent nature occurring specifically under load conditions and the systematic elimination of standard ignition components, what are the most probable remaining failure points? Seeking technical analysis of fuel delivery systems or overlooked ignition components that could manifest these specific symptoms.
Your 2014 Fleetwood Bounder's V10 random misfire at high RPMs on hills is likely caused by fuel delivery issues under load or remaining ignition components that haven't been replaced yet. The intermittent nature and specific conditions point to fuel pump weakness or injector problems.
Your 2014 Fleetwood Bounder 35K's V10 random misfire occurring only at 4-5000 RPMs on inclines is a classic symptom of fuel delivery issues under heavy load conditions. Since you've already addressed the most common ignition causes (plugs, some coils, MAF sensor), the problem is likely fuel-related or involves the remaining ignition components you haven't replaced yet.
First, have fuel pressure tested both at idle and under load simulation. The V10 requires 30-45 PSI at idle and should maintain pressure within 5 PSI of static pressure under load - a marginal pump will show normal pressure at rest but drop significantly under load.
Next, swap the 3 new coils from their current positions to cylinders that are showing misfires. If the misfire pattern changes location, you'll know the remaining original coils are failing. If the misfire stays random, it confirms a fuel delivery issue.
Consider having the fuel injectors flow-tested and cleaned professionally. The in-tank additives often can't resolve the types of deposits that build up in injectors over 49,000 miles of varied driving conditions.
Given that you've methodically addressed the basic causes, this issue requires more advanced diagnostics. A shop with RV experience and proper fuel pressure testing equipment under load conditions will be essential. The intermittent nature of your flashing check engine light makes this challenging to diagnose without the right tools and expertise with Ford V10 engines in motorhome applications.
The fact that your engine runs smooth otherwise and only misfires under these specific high-load conditions is actually helpful for diagnosis - it narrows the possibilities significantly to fuel delivery or heat-sensitive ignition components.
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