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Discussion Starter #1
Hey everyone I am new here (obviously), I have a 2013 MP412C with a tune and catless downpipes/exhaust. I was throwing some check engine codes (2177,2187,2195,2197) which my tuner addressed by changing an 02 sensor that seemed to be malfunctioning. This cleared the check engine codes but did not fix the hesitation issue. Any ideas? He is checking for boost leaks, but I was also thinking plugs/coils perhaps...maybe even fuel injectors. Any advice/help/input is greatly appreciated!
 

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Thank you for the reply guys, this issue only happens under heavy throttle, mostly only WOT...so first thing I did was have my tuner block off the ISG, and Ill be stopping by to see exactly how he went about this.

I did notice a hissing/high pitch whistle sound inside the cabin which got quieter when I lowered the ISG volume, so the ISG was my first assumption for a boost leak. He is also going to pull the plugs today and I'll ask him to check AFR's. I know we did change plugs right after the exhaust/tune upgrade...are ILKAR8E7 the correct plugs even with straight pipes/tune?
 

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2012 "Swipe" MP4-12C
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Plugs and coil packs are the best place to start. It is common for Cyl #5 spark plug gets water under the coilpack boot and will cause misfires. I pulled mine and it was rusty! Cyl #5 is the first cylinder behind/closest to the drivers seat (LHD cars of course)
 

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Hi, I now have this issue, was going for a spirited drive tonight and noticed the engine hesitating with a machine gun type sound at around 6k RPM anyone know what the issue is likely to be? the car has 19000 miles on it. I know the ISG hasnt been changed for some time, is it more likely to be a boost leak than coils/plugs? pretty sure it didnt do it before which makes me think its a leak...
 

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2012 "Swipe" MP4-12C
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Hi, I now have this issue, was going for a spirited drive tonight and noticed the engine hesitating with a machine gun type sound at around 6k RPM anyone know what the issue is likely to be? the car has 19000 miles on it. I know the ISG hasnt been changed for some time, is it more likely to be a boost leak than coils/plugs? pretty sure it didnt do it before which makes me think its a leak...
@mrvex,

Scan your ECU for any ODBii codes - even if the check engine light is off, you may have some codes which will help start your diagnosis of the issue
 

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no stored codes, however, the EML flashes about 3 mins into warm up sometimes and did log a 7/8 cylinder misfire which I reset but I didnt even feel any misfire then as it doesnt miss with normal driving, the two situations must be related, as I said the ISG has not been changed for a long time (27kkms) so it could be that not being able to hold the boost, the previous owner didn't change it for whatever reason. I am not convinced its plugs and coils tbh. just to add, I am a competent mechanic who can tune ecus and I used to work for mclaren on road cars in terms of mechanics but never came across this issue, I am confident that I know the issue but I was hoping if anyone else could chime in as well as I have not owned a mclaren before and owning and just maintaining one mechanically on the race track is two different things.

Before the misfire, the boost had already peaked as it was just over 6000 RPM when it occurred, where ever the issue is, it happened under pressure which makes me think it could be the ISG, i might turn it off as that will close the flap in the motor housing supplying the ISG's noise helping to seal the leak a bit, will also block it off to see if that helps if the first idea doesnt work, then will check all VAC lines to turbo and inlet manifold, then main boost pipes.. If they are all fine it will probably be a dodgy coil on 7/8.... If anyone knows of any other things that would be great.

Thanks
 

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2012 "Swipe" MP4-12C
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Swap cylinders 7 & 8 coil packs (from Bank 2) with any coil packs from any cylinder's 1-4 (Bank 1). this will let you know if it really is a bad coil pack. If your misfire code moves from 7 or 8 on Bank 2 over to the cylinders on Bank 1 then you just confirmed it was a bad coil pack.

If the misfire is still on 7 or 8 the replace the plugs there as well. If you still have the misfire on 7 & 8 after that let us know and we can dive deeper....
 

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According to McLaren tech manual, it can, I agree its more likely to be a coil though, plug I am not convinced. I will have a look on the weekend and report back. I dont think its any kind of fuel/ignition cut as i was rolling when I did the runs, probably dropped into 4th/3rd and went WOT
 

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For whatever reason, this has fixed itself... Mis hasnt come back since, for what its worth, if anyone is having misfires, check the gaps on the plugs, a smaller gap is going to make the car run better with less chance of misfires.
 
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