P0305 on Acura: How to Diagnose & Fix
Cylinder 5 Misfire Detected
3 Acura models · 3 documented issues · 2 critical · $100-$4,500 repair
P0305 on Acura by model: symptoms, diagnosis and fix
Like every C-series V6 Honda used in the 1990s and 2000s (Legend, NSX, CL, TL, RL all share the family), the RL's 3.5L C35A V6 has a distributor mounted at the back of the head and driven directly off the camshaft. Inside the distributor housing, an oil seal isolates the cam-driven shaft from the cap/rotor/electrical assembly above. By 100,000 miles the seal hardens, oil pressure forces engine oil past the shaft, and the cap fills with oil. Result: misfires (typically P0300 random plus individual cylinder codes P0301-P0306 since this is a V6), rough idle, hesitation. RepairPal explicitly lists distributor O-rings as one of the most common Acura RL oil leak points. The figure-8 oil cooler seal and oil filter housing gasket are the other two common leaks on this engine — diagnose carefully before assuming distributor. The C35A engine remained in the first-gen RL through the entire 1996-2004 production run, so this issue affects all years.
Common Symptoms
- Oil pooling inside the distributor cap when removed
- Engine misfires, especially under load or after warm-up
- Check engine light with P0300 random misfire or P0301-P0306 single-cylinder
- Rough idle that smooths out with throttle
- Visible oil at the rear of the engine, dripping down the back of the block
How to Fix
There is no replaceable seal inside the distributor — the seal is between the rotating shaft and the bearing inside the cast housing. The only fix is replacing the whole distributor assembly. OEM Honda runs $400-700; Cardone remanufactured runs $150-250. While the distributor is out, also replace the distributor cap, rotor, and ignition wires — they're cheap and you're already at the parts. Inspect the cap and rotor on the old unit for oil contamination to confirm distributor was the source. If you also see leaks elsewhere (figure-8 cooler seal, oil filter housing), address those at the same time — they share access path. Total job: 2-3 hours independent shop.
Owner tips & cautions
- TipReplace cap + rotor + ignition wires at the same time as the distributor. You're already there. Saves a future labor cycle.
- WarningDon't assume distributor without inspection. RepairPal also lists the oil cooler 'figure-8' O-ring and oil filter housing gasket as common RL leaks. Pull the cap and check for oil before buying the distributor.
Sources for this issue (2)
The second-generation RDX switched to the naturally aspirated J35 3.5L V6 with Variable Cylinder Management, and inherits the VCM failure pattern documented across Honda's V6 fleet. When VCM deactivates the rear bank, those cylinders run cool and unfired; oil is drawn past the rings and valve guides, glazes the bores and coats the plugs. Owners report the rear three spark plugs oil-fouled and carbon-loaded at service intervals, misfires on the rear bank, elevated oil consumption between changes (commonly a quart or more per 3,000-5,000 miles), and eventually ring-land carbon buildup that makes the consumption self-reinforcing. Honda's earlier VCM oil-consumption class action and warranty extension covered the 2008-2013 J35 fleet; RDX owners report the same mechanism on this platform. This is a VCM/J35 issue only — it does not apply to the 2007-2012 K23A1 turbo four or the 2019+ 2.0T.
Common Symptoms
- Oil level dropping a quart or more between changes
- Rear bank spark plugs oil-fouled at inspection
- Misfire codes on cylinders 1/3/5 (rear bank)
- Rough idle or stumble after cruising
- Blue smoke on startup or hard acceleration
- Low oil pressure light in late stages
How to Fix
Check oil level between changes and expect to top up. Replace all six plugs with the correct OEM-spec iridium plugs at shortened intervals (many owners go to roughly 60,000 miles rather than waiting out the full interval) and inspect the rear three for oil fouling as the diagnostic tell. Where documented consumption exists, the dealer procedure is a measured oil-consumption test followed by piston-ring replacement under any applicable warranty extension. Many owners fit a VCM-disabling controller (an S-VCM/VCM-tuner type device that holds coolant temperature so the engine stays out of 3-cylinder mode) to stop the mechanism progressing — an owner remedy, not a factory-endorsed one, and it can affect emissions compliance. No RDX-specific recall exists.
Sources for this issue (3)
The 3.7L J37 V6 used in many TL SH-AWD models has a documented pattern of excessive oil consumption, sometimes leading to low oil level warnings, misfires, and spark plug fouling. Acura/Honda issued warranty extensions and service information for affected V6 engines in this family due to piston ring-related oil consumption. Owners often notice the engine using significant oil between changes, and if ignored, the condition can progress to rough running and catalyst damage risk.
Common Symptoms
- Oil level drops between oil changes
- Low oil warning or dipstick reading low
- Misfire under load or at idle
- Fouled spark plugs
- Blue smoke on startup in some cases
How to Fix
Monitor oil level closely and document consumption over a measured interval. Diagnosis typically includes checking for external leaks, inspecting plugs for oil fouling, and performing the manufacturer oil consumption test procedure. Repairs may involve updated pistons/rings under prior warranty programs or ongoing oil top-offs if consumption is mild and the vehicle is outside assistance coverage.
Owner tips & cautions
- TipCheck oil every 1,000 miles on the 3.7L, especially if service history is unknown; many owners avoid engine damage by topping off early.
Sources for this issue (2)
P0305 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0305 mean on a Acura?
P0305 stands for "Cylinder 5 Misfire Detected." This code means the engine control module detected a misfire on cylinder number 5, meaning that cylinder is not burning its air-fuel mixture properly on some combustion cycles. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder fails to fire correctly. A misfire wastes fuel, can make the engine run rough or shake, and dumps unburned fuel into the exhaust, which can overheat and damage the catalytic converter. It generally points to a problem with spark, fuel delivery, or compression specifically affecting cylinder 5. On Acura it is documented across 3 models: RL, RDX, TL.
What are the most common causes of P0305?
The most common causes of P0305 are: Worn or fouled spark plug on cylinder 5, Failed ignition coil or coil pack for cylinder 5, Faulty or clogged fuel injector on cylinder 5, Vacuum or intake air leak affecting that cylinder, Bad spark plug wire or boot (on applicable engines), Low compression from worn rings, valves, or head gasket, Carbon buildup or sticking valve on cylinder 5, Lean or rich fuel condition affecting the cylinder. The specific cause varies by vehicle.
How much does it cost to fix P0305 on a Acura?
Published repair estimates on Acura range from $100 to $4,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0305 on a different make?
View P0305 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.