Hello, I hope all is well. My 1999 ML430 misfires with codes P0304 and P0307. I have recently replaced spark plugs, air filter, and fuel pump. I am assuming it is an issue with the ignition coils but the car doesn't typically begin to misfire badly unless harshly accelerated, but if the car is restarted it doesn't shake as much. Any thoughts? I also have codes P0130 and P0150 for the oxygen sensors but they seem to be working fine.
Heres the data I got using my iCarsoft MB 2.0
Smooth Data
Vehicle:
Customer:
Operator:
Date(D/M/Y):15/12/2020
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BENZ_EN_TEST_00007>ML(163)>Gasoline>163.172 - ML 430>Smart Scan>ECM - Engine Control Module(ME2-SFI)>View Data>Smooth engine running:
Total Frames: 10 , Supported Items: 10
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Frame 1/10:
Engine speed ----- 699rpm
Smooth running of cylinder 1 ----- 1.02L/s²
Smooth running of cylinder 5 ----- 0.77L/s²
Smooth running of cylinder 4 ----- 0L/s²
Smooth running of cylinder 2 ----- -0.51L/s²
Smooth running of cylinder 6 ----- 0L/s²
Smooth running of cylinder 3 ----- 1.02L/s²
Smooth running of cylinder 7 ----- -0.26L/s²
Smooth running of cylinder 8 ----- -0.51L/s²
Irregular running shutoff threshold ----- 4.86L/s²
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Frame 2/10:
Engine speed ----- 709rpm
Smooth running of cylinder 1 ----- 1.02L/s²
Smooth running of cylinder 5 ----- 3.07L/s²
Smooth running of cylinder 4 ----- 0L/s²
Smooth running of cylinder 2 ----- -1.28L/s²
Smooth running of cylinder 6 ----- -0.51L/s²
Smooth running of cylinder 3 ----- 0.51L/s²
Smooth running of cylinder 7 ----- -0.26L/s²
Smooth running of cylinder 8 ----- -0.51L/s²
Irregular running shutoff threshold ----- 4.86L/s²
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Frame 3/10:
Engine speed ----- 706rpm
Smooth running of cylinder 1 ----- 0.77L/s²
Smooth running of cylinder 5 ----- 1.79L/s²
Smooth running of cylinder 4 ----- 0L/s²
Smooth running of cylinder 2 ----- 0L/s²
Smooth running of cylinder 6 ----- -0.26L/s²
Smooth running of cylinder 3 ----- 2.30L/s²
Smooth running of cylinder 7 ----- -0.26L/s²
Smooth running of cylinder 8 ----- -0.51L/s²
Irregular running shutoff threshold ----- 4.60L/s²
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Frame 4/10:
Engine speed ----- 681rpm
Smooth running of cylinder 1 ----- 0.77L/s²
Smooth running of cylinder 5 ----- 3.07L/s²
Smooth running of cylinder 4 ----- 0L/s²
Smooth running of cylinder 2 ----- -0.77L/s²
Smooth running of cylinder 6 ----- -0.26L/s²
Smooth running of cylinder 3 ----- 0L/s²
Smooth running of cylinder 7 ----- -0.77L/s²
Smooth running of cylinder 8 ----- 0L/s²
Irregular running shutoff threshold ----- 4.86L/s²
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Frame 5/10:
Engine speed ----- 698rpm
Smooth running of cylinder 1 ----- 0.51L/s²
Smooth running of cylinder 5 ----- 0L/s²
Smooth running of cylinder 4 ----- -0.51L/s²
Smooth running of cylinder 2 ----- 0L/s²
Smooth running of cylinder 6 ----- -0.77L/s²
Smooth running of cylinder 3 ----- 1.79L/s²
Smooth running of cylinder 7 ----- 0L/s²
Smooth running of cylinder 8 ----- -0.77L/s²
Irregular running shutoff threshold ----- 4.60L/s²
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Frame 6/10:
Engine speed ----- 691rpm
Smooth running of cylinder 1 ----- 0L/s²
Smooth running of cylinder 5 ----- 2.81L/s²
Smooth running of cylinder 4 ----- 0L/s²
Smooth running of cylinder 2 ----- -0.51L/s²
Smooth running of cylinder 6 ----- -0.77L/s²
Smooth running of cylinder 3 ----- 1.02L/s²
Smooth running of cylinder 7 ----- 0L/s²
Smooth running of cylinder 8 ----- -0.26L/s²
Irregular running shutoff threshold ----- 4.60L/s²
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Frame 7/10:
Engine speed ----- 699rpm
Smooth running of cylinder 1 ----- 1.02L/s²
Smooth running of cylinder 5 ----- 0.51L/s²
Smooth running of cylinder 4 ----- 0L/s²
Smooth running of cylinder 2 ----- -0.51L/s²
Smooth running of cylinder 6 ----- -0.26L/s²
Smooth running of cylinder 3 ----- 0.51L/s²
Smooth running of cylinder 7 ----- -0.51L/s²
Smooth running of cylinder 8 ----- 0L/s²
Irregular running shutoff threshold ----- 4.60L/s²
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Frame 8/10:
Engine speed ----- 674rpm
Smooth running of cylinder 1 ----- 0.51L/s²
Smooth running of cylinder 5 ----- 1.28L/s²
Smooth running of cylinder 4 ----- 0L/s²
Smooth running of cylinder 2 ----- 0L/s²
Smooth running of cylinder 6 ----- -1.02L/s²
Smooth running of cylinder 3 ----- 2.05L/s²
Smooth running of cylinder 7 ----- 0L/s²
Smooth running of cylinder 8 ----- 0L/s²
Irregular running shutoff threshold ----- 4.60L/s²
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Frame 9/10:
Engine speed ----- 679rpm
Smooth running of cylinder 1 ----- 0.26L/s²
Smooth running of cylinder 5 ----- 0.51L/s²
Smooth running of cylinder 4 ----- -1.02L/s²
Smooth running of cylinder 2 ----- -0.77L/s²
Smooth running of cylinder 6 ----- 0L/s²
Smooth running of cylinder 3 ----- 0L/s²
Smooth running of cylinder 7 ----- 0L/s²
Smooth running of cylinder 8 ----- 0L/s²
Irregular running shutoff threshold ----- 4.60L/s²
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Frame 10/10:
Engine speed ----- 682rpm
Smooth running of cylinder 1 ----- 0.26L/s²
Smooth running of cylinder 5 ----- 2.81L/s²
Smooth running of cylinder 4 ----- -0.51L/s²
Smooth running of cylinder 2 ----- -0.51L/s²
Smooth running of cylinder 6 ----- -0.26L/s²
Smooth running of cylinder 3 ----- 2.05L/s²
Smooth running of cylinder 7 ----- 0L/s²
Smooth running of cylinder 8 ----- 0L/s²
Irregular running shutoff threshold ----- 4.60L/s²
OBD Live Data Test
Frame 8/8:
Fuel system 1 status ----- CL
Fuel system 2 status ----- CL
Calculated LOAD Value ----- 18.8%
Engine Coolant Temperature ----- 77°C
Short Term Fuel Trim B1 ----- 0.0%
Long Term Fuel Trim B1 ----- 0.8%
Short Term Fuel Trim B2 ----- -1.6%
Long Term Fuel Trim B2 ----- 1.6%
Intake Manifold Absolute Pressure ----- 32.0kPa
Engine Speed (Revolutions Per Minute of crankshaft) ----- 640rpm
Vehicle Speed ----- 0km/h
Ignition Timing Advance for #1 Cylinder ----- -11.5°
Intake Air Temperature ----- 31°C
Air Flow Rate from Mass Air Flow Sensor ----- 5.10g/s
Absolute Throttle Position ----- 5.5%
Commanded Secondary Air Status ----- OFF
Oxygen Sensor Output Voltage (B1-S1) ----- 0.525V
Short Term Fuel Trim (B1-S1) ----- 0.0%
Oxygen Sensor Output Voltage (B1-S2) ----- 0.735V
Short Term Fuel Trim (B1-S2) ----- 99.2%
Oxygen Sensor Output Voltage (B2-S1) ----- 0.740V
Short Term Fuel Trim (B2-S1) ----- -0.8%
Oxygen Sensor Output Voltage (B2-S2) ----- 0.710V
Short Term Fuel Trim (B2-S2) ----- 99.2%
Idle Data
BENZ_EN_TEST_00007>ML(163)>Gasoline>163.172 - ML 430>Smart Scan>ECM - Engine Control Module(ME2-SFI)>View Data>Test values at idle speed:
Total Frames: 3 , Supported Items: 20
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Frame 1/3:
Temperature of coolant ----- 56°C
Temperature of intake air ----- 22°C
Engine speed ----- 660rpm
Air mass ----- 16kg/h
Throttle valve angle ----- 4.09°
Ignition angle ----- 12.80°
Injection time, right ----- 3.26ms
Injection time, left ----- 3.18ms
Signal sensor at camshaft ----- Signal Present
Battery voltage ----- 13.93V
On/off ration of purge control ----- 11.76%
HFM-SFI voltage(Engine at idle) ----- 1.43V
HFM-SFI voltage(Engine not running) ----- 1.43V
Air conditioning ----- OFF
Engine oil level ----- OK
Idle speed detection ----- ON
Purge control ----- ON
Oil temperature ----- 37°C
Oil quality ----- 2.33
Fuel tank level ----- 34L
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And the Freeze Frame Data for P0300
OBD_EN_TEST_00002>Freeze Frame:
Supported Items: 12
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Frame 1/1:
DTC that caused required freeze frame data storage ----- P0300
Fuel system 1 status ----- CL
Fuel system 2 status ----- CL
Calculated LOAD Value ----- 19.2%
Engine Coolant Temperature ----- 74°C
Short Term Fuel Trim B1 ----- 1.6%
Long Term Fuel Trim B1 ----- 1.6%
Short Term Fuel Trim B2 ----- 1.6%
Long Term Fuel Trim B2 ----- 2.3%
Intake Manifold Absolute Pressure ----- 30.0 kPa
Engine Speed (Revolutions Per Minute of crankshaft) ----- 1900 rpm
Vehicle Speed ----- 87 km/h
I tried to trim out all of the unnecessary stuff from the data. Thank you in advance.
Hello and Merry Christmas. I love analyzing data... and very helpful. You have a very good A/F (LTFT values). Your coolant temp temp is a tad low, not related to this issue likely but something I'd want to investigate.
Ok, I'd replace the upstream O2's as they start responding slower over time and the ecm has to have accurate data in appropriate time. OEM only for merc. Also, if you are having misfires some raw fuel is getting into exhaust and not doing your O2's or cats any good. While they are out, I'd go ahead and check pressure at the O2 bung just so I would have additional knowledge on cat condition.
MAF flow is a tad wacky so I would clean and consider replacing (oem only) after the below is evaluated.
Now a coil pack going bad is likely and can cause O2 and cats to degrade, so swap packs around and see if you can get the misfire to change to different cylinders. Do O2's first. So coils go bad and degrades O2's and age of O2's and maf may be contributing factor. 99% one or combo of these will fix you up. But as always, there are other possibilities, just less likely. And I commend you as you've obviously taken care of it. Pls keep use posted.
Thank you for the response!! I bought this iCarsoft because for the price I know its 100% worth it for what you get back but I haven't learned how to analyze data yet but thank you!! The coolant temperature is low because my dad commutes only a few minutes to and from work so the car isn't running at full operating temperature all of the time so thats why that is there. Changing the o2s are probably a good idea anyway since the car is over 20 years old with +200k miles. Will definitely explore that and coil swapping. I'll try to update you if I dont forget 😆 . Thank you so much!
Tell your Dad if he'll let it warm up a tad longer before starting off, it will help in vehicle longevity (ideally, be in closed loop before driving). But splitting hairs... I think you understand why tho and keep learning/studying 🙂
edit. I'd replace maf too (age/miles) for good measure, use only oem or Bosch... I don't recommend Bosch only because there are a lot of counterfeits out there, but if genuine they are 100% fine too.
I had similar issue on my Honda. Changed several things. I changed the timing belt and found it was off one tooth. Might give the valve timing a look as it can cause issues if it's not right on. After the timing belt change it ran like new. Also would look at the EGR valve. Good luck.
The timing data is something interesting I haven't fully understood yet. But these engines are interference and the timing chain on my 2004 C320 with the same engine slaps for a few seconds when its cold but it runs perfectly fine.
since you have specific cylinder codes swap the coils (if possible) and fuel injectors with cylinders not giving a code and see if the code follows or stays with the same cylinders. low compression/vacuum leaks are other things to look for.
Planning on doing the coil swap strategy. I already did it with a cylinder 2 misfire and swapped 2 and 1 but the misfire went away in its entirety so that was interesting 😆