Hey y’all, I am looking for some guidance with finding the cause of a persistent misfire that has been ongoing for over six months and remains unresolved even after correcting a confirmed burnt exhaust valve.

Approximately six months ago, I purchased a used 2013 Honda Accord with a 2.4L, K24W1, 4CYL, Earthdreams Engine. It had a severe misfire and blinking check engine light. At the time, the cause of the misfire was unknown. I initially replaced the spark plugs and ignition coils with no improvement. I then replaced all fuel injectors, but the engine continued to misfire. The vehicle would not rev past 3,000 RPM and exhibited severe stuttering and shaking, particularly when accelerating or placing it in reverse or drive. The vehicle behaved as if it were in limp mode.

I then proceeded with mechanical testing. A compression test that I did revealed that cylinder 4 had approximately 15 psi, while the remaining cylinders were within normal range. I then performed a leak-down test, which showed air escaping through the exhaust (tailpipe) on cylinder 4. Based on these results, I concluded there was a burnt exhaust valve.

I disassembled the engine, removing the valve cover, timing components, and surrounding parts to access the cylinder head. Upon removal of the head, I confirmed that the exhaust valve on cylinder 4 was severely burnt, with a large hole through the valve. The intake valve on cylinder 4 also showed damage, including jagged edges and poor seating, so I replaced both the intake and exhaust valves on that cylinder.

To ensure the cylinder head was fully corrected, I sent it to a professional machine shop. The machine shop performed the following work: all valves were lapped, valve stem heights were checked, new valve stem seals were installed, and the head was checked for flatness and confirmed to be within specification. No issues were reported by the machine shop.

After receiving the head back, I carefully reassembled the engine. Cam timing was verified during installation, and no shortcuts were taken during reassembly.

Following the reassembly, I performed another compression test. Compression is now strong and consistent, showing over 180 psi on all cylinders. Despite this fix, the original issues still remain unchanged. The engine still misfires, the check engine light continues to blink, the engine will not rev past approximately 3,000 RPM, and it shakes heavily at idle and when placed in Drive or Reverse.

At this point, I don’t know where to look. I am seeking input from anyone who might have an idea or know what to do next.

 

i have a 4 cylinder Honda sedan that is misfiring and I cant figure out why. I already did excessive work to it including. replacing spark plugs, ignition coils, injectors, verified timing, and even a replaced a burnt valve. the whole engine is all put back together and still misfires. took the car to oreileys and autozone and their obd-II scans recommend that I change the cranksahft position sensor.

Any tips or ideas on how to fix this misfire would be much appreciated.

car has 90k miles btw which is crazy to me that it's doing this.

 

Seems like you picked all the low hanging fruit that most DIYers can hope to accomplish.

I d say take into a shop, as you'll need testing equipment and experience to figure out the problem from here......

 

Really!? I don't see what more they could possibly do in the shops. I feel like I'm right at the finish line of fixing this car. just have to figure out one small thing. Do you know of anything else i can try to fix this stubborn car?

 

Yet these types of issues are solved daily. You dont know what you dont know.

You need a scan tool with full data streams and bi-directional controls.
You need to have a thorough understanding and be able to interpret the data you acquire from the scanner.
You need an oscilloscope with various pressure transducers and amp clamps and again experience and knowledge to interpret the results.
You need an exhaust gas analyzer.

At least, this is how this problem would be approached in my shop.
Sorry I dont have better advice that what you've already attempted. Like I said,you hit on all the obvious points already.

I respect the diligent DIYer.

I DIY plumbing, electrical, and other home repairs around my house. Im mostly successful.

But sometimes I have to call in a pro......

 

what were all the codes?

 

THESE ARE ALL THE SCANS AND CODES I GOT IN A DETAILED TIMELINE

Initial scan – BEFORE teardown (≈6 months ago)

• P0304 (Stored / Permanent / Pending) — Cylinder 4 misfire detected
  
• P0135 (Permanent) — O2 sensor heater circuit malfunction (Bank 1 Sensor 1)
  

After engine work – O’Reilly scan #1

• P0301 (Pending) — Cylinder 1 misfire detected
  
• P0302 (Pending) — Cylinder 2 misfire detected
  
• P0300 (Pending) — Random/multiple cylinder misfire detected
  
• P0302 (Permanent) — Cylinder 2 misfire detected
  
• P0304 (Permanent) — Cylinder 4 misfire detected
  
• P0353 (Permanent) — Ignition coil circuit malfunction (Cylinder 2 – intake side)
  
• P0354 (Permanent) — Ignition coil circuit malfunction (Cylinder 2 – exhaust side)
  

O’Reilly scan #2 – After swapping ignition coils #2 and #3

• P0302 (Stored) — Cylinder 2 misfire detected
  
• P0102 (Stored) — Mass air flow (MAF) sensor low
  
• P0302 (Pending) — Cylinder 2 misfire detected
  
• P0302 (Permanent) — Cylinder 2 misfire detected
  

AutoZone scan #1

• P0300 — Random/multiple cylinder misfire detected
  
• P0301 — Cylinder 1 misfire detected
  
• P0302 — Cylinder 2 misfire detected
  
• P0304 — Cylinder 4 misfire detected
  
• P0353 — Ignition coil circuit malfunction (Cylinder 2 – intake side)
  
• P0354 — Ignition coil circuit malfunction (Cylinder 2 – exhaust side)
  

AutoZone scan #2 – After same coil swap

• P0302 — Cylinder 2 misfire detected
  
• P0102 — Mass air flow (MAF) circuit low input
  
• P0304 — Cylinder 4 misfire detected
  
• P0353 — Ignition coil circuit malfunction (Cylinder 2 – intake side)
  
• P0354 — Ignition coil circuit malfunction (Cylinder 2 – exhaust side)
  

 

Man what is with all the ai post...

Have you looked at the maf sensor?

 

yeah took it off amd cleaned it to make the situation clear

 

You will need to find the issue causing the maf code first.

 

thats what i mean i took it off cleaned it and reconnected it. the code for maf is gone. i have a misfire in cylinder 2 and 4 apparently. the P0353 and 0354 codes are still popping up for the coil ignition coil on cylinder 2. i know it aint a coil they recommended me to change the crankshaft position sensor at the autopart store. should i try that. I also heard you can relearn the crnkshaft pattern in the computer. how about doing that?

 

Clear all the codes, swap the cylinder 2 coil with another and drive again until codes show up.

 

Alright, here is where were at so far,

Following y'all suggestions unfortunately did not seem to help any bit. I seen some things on the internet about relearning the Crankshaft pattern and resetting the ECM. I figured at this point why not Ill try that and hope for the best. I bought a FOXWELL NT510 obd2 scanner specifically for honda/acura. I proceeded with the relearn and reset that did not solve my problem you guys. I then bought a crank shaft position sensor oem and installed it since thats what the auto parts stores recommend and that did not make a difference $80 down the drain. the codes were erased so I went ahead and did a thorough scan. What came out was: P0102 MAF SENSOR VOLTAGE LOW, P0172 FUEL SYSTEM TOO RICH B1, P0301 CYLINDER 1 MISFIRE, and P0300 RANDOM MISFIRE 4 in total!

Additionally guys, I have noticed a excessive gas smell coming from the car. Like you literally could pass out from the amount of raw fuel this misfiring car puts in the air. At this point I am ruling out any singular mechanical components such as, coils, spark plug, injector, valve etc. Why? because this misfire is not persistent in one single cylinder, it moves from one to another. (Every time i scan the codes there is a random misfire code or different cylinder misfire there is never one single cylinder consistently misfiring. Its obvious im too rich and can't figure out why. this car reeks of gas from a mile away, I put $15 of gas in a 4 cylinder k24w1 2.4l that should get ~30mpg, This car burnt through all that gas which was close to nearly half a tank in 2 days at idle!!!

i tried running it with maf sensor disengaged and it ran the same. I dont know what the hell it can be man this car is really testing my patience if you guys have any other suggestions that may help me solve this mystery i would appreciate it. (there ain't a good shop in my area either so im on my own)

 

Where are you located?

 

New Mexico I live in the mountains near ruidoso.

 

check engine coolant temperature sensor and fuel pressure regulator

 

Arguably one of the greatest automotive diagnostic minds in the country works out of Albuquerque. However, he doesn't serve the general public, only repair facilities.

Ive reached out and asked if he has any recommendations for a shop in your area.....

 

Says he doesn't know of any good shops in your area.

He recommends Taz Auto in Albuquerque if you can make it out there......

 

I don't know if this may help any of you guys draw a conclusion to what is the problem. My scan tool has a function that allows me to view live data while the engine is running, here a list of data points I figured might be helpful. I can't interpret much of this stuff. Hopefully you guys can read this and have an idea of what may be the primary issue.

Temperature Data (Warm Idle ~800 RPM)

• IAT (Start): 28°C
  
• IAT Sensor (Current): 27°C
  
• IAT Voltage: 2.74 V
  
• ECT (Start): 64°C
  
• ECT Sensor 1: 71°C (1.00 V)
  
• ECT Sensor 2: 20°C (3.12 V)
  
• Catalyst Temp: 478.8°C
  
• Estimated Battery Temp: 18°C
  

Fuel System

• Direct Injection Fuel Pressure: 3870–4000 kPa
  
• Fuel Pressure Sensor Voltage: 1.15 V
  
• Injector Pulse Width: 1.44 ms
  
• AF Lambda Commanded: 1.01
  
• AF Lambda Actual: 0.90
  
• AF FB (STFT): 0.69
  
• AF FB AVE (LTFT): 0.77
  
• Air Fuel Ratio: 13.02–14.52
  
• Fuel Consumption (Idle/Stop Status): 8439 cc
  
• Fuel Consumption (City): 4533 cc
  
• Fuel Level: 7.84–8.10%
  

Airflow / Intake Data

• MAF Voltage: 1.45 V
  
• MAF Flow: 5.40 g/s
  
• MAP: 38.00 kPa
  
• MAP (Hi Res): 301.40 mmHg
  
• MAP Voltage: 1.18 V
  
• Barometric Pressure: 88.00 kPa
  
• Baro Voltage: 2.57 V
  
• FTP Sensor: -0.13 kPa
  
• FTP Sensor (Fine): 16264.50 Pa
  

Oxygen / A/F Sensors

• AF Sensor Signal (+): 2.20
  
• AF Sensor Signal (−): 1.82
  
• AF Sensor Current: 0.26 mA
  
• AF Sensor Impedance: 38 ohm
  
• HO2S S1 Heater: ON
  
• HO2S Heater Duty: 87%
  
• HO2S S2 Voltage: 0.92 V
  
• HO2S S2 Output Voltage: 2.47 V
  
• HO2S S2 Heater Current: 0.89 A
  
• HO2S S2 Heater: ON
  

Misfire / Crank / Cam Data

• Misfire Driving Cycle: 1.00
  
• CKP Noise: 0
  
• CKP No Pulse: 0
  
• CMP A Noise: 60
  
• CMP A No Pulse: 50
  
• CMP B Noise: 0
  
• CMP B No Pulse: 5
  
• CKP Pulser F/B Learn: Not Completed
  
• Idle Learn: Not Completed
  

Electrical System

• Alternator Circuit: 12.5
  
• Alternator L Signal: Low
  
• Estimated Battery Resistance: 9.30 mΩ
  
• ELD (Electrical Load): 16.50 A
  

Throttle / Drive-by-Wire

• Throttle Valve: 3.90°
  
• Target Throttle: 3.91°
  
• Idle Target Throttle: 3.94°
  
• TP Sensor A: 0.74 V
  
• TP Sensor B: 1.59 V
  
• APP Sensor A: 0.96 V
  
• APP Sensor B: 0.47 V
  
• DBW Stuck Ratio: 28.24%
  
• Engine Speed: 800 RPM
  

Other Data

• Spark Advance: 8–14.5°
  
• Knock Retard: 0.00
  
• Knock Sensor Drag: 2.51 V
  
• Knock Control: 1.50
  
• VTEC Pressure Switch: ON
  
• VTEC Solenoid: OFF
  
• Slip Ratio (Clutch/Start): 96–100%
  
• A/F Imbalance Measurement: 0.00
  

Just to recap where the car is at it’s still misfiring even after everything that’s been done. Plugs, coils, injectors, timing verified, burnt valve repaired, ECM reset with crank relearn, and even a new crankshaft position sensor. Compression is strong across all cylinders, so mechanically it should be sound. Despite that, it’s still running very rough. It won’t rev properly, shakes at idle, and it’s running extremely rich. The raw fuel smell is strong, like it’s dumping gas. Current codes are P0102 (MAF voltage low), P0172 (system too rich), P0301 (cylinder 1 misfire), and P0300 (random misfire). What’s odd is the misfire keeps moving. Before it was cylinders 2 and 4, now it’s mainly 1.
I’m just trying to figure out the right next step instead of continuing to throw parts at it.

 

You need to find out why it's throwing the maf code still. If it cant properly read the airflow coming in it's just going to revert to dumping fuel for safety.

 

What things would you suggest me to look at that may be throwing the MAF code?

 

The data you posted is static and doesn't serve much purpose. The data needs to be recorded under varying load conditions.

Its also in numerical form, where it needs to be graphical, and for some reason you are missing the calculated or absolute load PID, which is an important PID for drivability issues.

With that said, the only thing that stands out is the fact that the MAF sensor is reading entirely too high at idle.(which would absolutely cause a rich condition)

If it were reading too low, there could be a few different reasons, but a too high reading is almost always a bad MAF.

I suppose you may eventually stumble onto a solution, but I still wouldn't replace any parts based on internet wisdom.

Especially from the ding dongs on this forum......

 

The factory service manual.

 

Well folks, I've decided to just back off and allow the mechanics to take a crack at this car, I'll be taking it in this Friday. hopefully they find this mysterious issue right away with all their high dollar gizmos.
thanks for yalls help.

 

Hope they don't just plug in a scanner, tell you your maf is bad and charge you $200 for diagnostic.