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Discussion Starter #1
Is anyone getting random cylinder misfires on their 12C? I have it happening just after the engine is warmed up and I have to idle at a redlight...quite annoying. I get a blinking check engine light that occasionally goes solid. It clears after a couple of starts or I clear it from my Dash Command App and a Pixi II ODB cable (at the instruction of my McLaren dealer).

I don't like this constantly occurring and wanted the groups 2 cents.
 

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sorry to hear snowhorn. never had it, and haven't heard of the issue before now. that sounds like something the dealer should run a heavy diagnostic. :(
 

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Is anyone getting random cylinder misfires on their 12C? I have it happening just after the engine is warmed up and I have to idle at a redlight...quite annoying. I get a blinking check engine light that occasionally goes solid. It clears after a couple of starts or I clear it from my Dash Command App and a Pixi II ODB cable (at the instruction of my McLaren dealer).

I don't like this constantly occurring and wanted the groups 2 cents.
I've had that off and on for a few months now. I mentioned it to my dealer and they looked into it but there wasn't a clear solution and it still occurs every now and again. Coincidentally it actually occurred for me today at a stop light. Sorry I don't have more info for you, but if you find anything else out, it would be great to hear.
 

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Since the dealer is not demanding an immediate return for diagnostics, my conclusion would be towards an over eager OBD II channel - bad gas maybe?
 

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Discussion Starter #5
The dealer said they thought bad gas but this is a recurrent problem over 4 months. FWIW I only use Shell VPower 93 Octane (same as 98 RON). The issue is more a nuisance than a serious issue as it does not reduce power or give me the death warning telling me to call the dealer. It is just a disconcerting feeling every time the check engine light starts to blink.

I just had the Ver 12 software update which fixed several glitches for the better but sadly this was not one of them. I will keep you all posted if I find a solution.
 

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yes yes ! i keep getting this . I get lean codes and flashing engine light . Car runs fine but when i turn car on i get this . Dealer cant figure it out and keeps changing parts with no solution .

I already did all gas even 100 oct . and all fuel additives . Changed plug they even replaced a few injectors . and coil packs
 

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Did they change the oxygen sensors? Would be my guess....

yes yes ! i keep getting this . I get lean codes and flashing engine light . Car runs fine but when i turn car on i get this . Dealer cant figure it out and keeps changing parts with no solution .

I already did all gas even 100 oct . and all fuel additives . Changed plug they even replaced a few injectors . and coil packs
 

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If you are running lean, it would nice to know if the ECU runs off of MAF readings.
 

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Discussion Starter #12
Here are the codes:
P0300 - Random/Multiple Cylinder Misfire Detected
P0308 - Cylinder 8 Misfire Detected
P0305 - Cylinder 5 Misfire Detected
P0307 - Cylinder 7 Misfire Detected

This always clears itself after a day or two or if I reset the CEL
 

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Here are the codes:
P0300 - Random/Multiple Cylinder Misfire Detected
P0308 - Cylinder 8 Misfire Detected
P0305 - Cylinder 5 Misfire Detected
P0307 - Cylinder 7 Misfire Detected

This always clears itself after a day or two or if I reset the CEL

OMG that's exactly what i get i just read the codes but my hand held wont allow me to delete . exact Cylinders exact .. has to be something else. we cant be getting exact codes.
 

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And they are on both banks too... That eliminates, O2 sensors, MAFs, anything unique to one bank or the other... I guess they could all fail at the same time, but not likely. And 2 owners with the exact codes/cylinders?

My money is on the IRIS :D
 

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Discussion Starter #15
And they are on both banks too... That eliminates, O2 sensors, MAFs, anything unique to one bank or the other... I guess they could all fail at the same time, but not likely. And 2 owners with the exact codes/cylinders?

My money is on the IRIS :D
What if this falls into a certain Vin batch? I am 424.
 

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I wonder if it's the catalytic converter - which in the US is under warranty for 7 years.

Could be a loose converter gasket etc. causing a leak.
 

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It just hit me, remembering a white sheet on the engine posted in another thread, there a 4 knock sensors on the engine and one is directly between cyl 5&7. Depending on the fuel delivery system and hot spots in the engine there could be an intermittent knock at the front of the engine, specifically around 1 or 2 cyl that knocks a little under acceleration when timing is being advanced. Cyl 8 may be sending the knock from 7, but doubtful. Many engines have hot / lean cylinders and require a custom tune to fatten up one or 2 cylinders to prevent this lean/ knock condition. I'd like to think McL would have found this during development. Fuel flow and heat are the root causes of this if this is intact the issue. A knock can be interpreted as a misfire by the ECU.

Just thinking out loud.
 

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A real time ODB2 scanner like the Auto X-ray will show the faults as they occur. It can also data log and load to a PC for analysis. You can leave it plugged into the car while you drive around. This kind of stuff is fun but I know it's under warranty
 
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