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Got a Mclaren today, 2013, full service done by Mclaren 100 miles ago. When I cold start my RPM jumps 500-1k up and down up and down shuddering almost as if its starving for fuel. No lights, and Mclaren says everything checked and and nothing should be weird, they said maybe an oil cap or something small. Anyone else experience this! Please help tried to get a video and can't, it wont do it again until its fully ice cold the engine. If I rev it the rpm levels off and it stops doing the quick up down up down RPM revs on its own.
 

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Got a Mclaren today, 2013, full service done by Mclaren 100 miles ago. When I cold start my RPM jumps 500-1k up and down up and down shuddering almost as if its starving for fuel. No lights, and Mclaren says everything checked and and nothing should be weird, they said maybe an oil cap or something small. Anyone else experience this! Please help tried to get a video and can't, it wont do it again until its fully ice cold the engine. If I rev it the rpm levels off and it stops doing the quick up down up down RPM revs on its own.
Have dealer check ISG diaphragm.
 

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My 2013 did this pretty regularly with cold start ups, and McLaren Atlanta (where car came from) said it was just a common quirk on some cars. However , I had my doubts, because sometimes it would idle so rough that the Check Engine light would blink for a few seconds. It always went away within a minute. Then, last year, I installed an intake sound generator delete plate, and it hasn’t happened since.
 

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Ok I will change that part to start, and check all caps make sure nobody left like a gas cap or something loose.
Good, the ISG develops a small (rust) hole in the diaphragm. This allows unmetered air to enter the manifold which leans out the choke Fuel to Air ratio on a cold engine — gives the rough stumble. As the motor heats up there is less effect but in time the hole gets larger and the problem gets much worse for a broader heat range. If you buy the aluminum block off plate from @XPRD that will be a permanent fix for this issue. Hope this is the problem and that you are able to fix it soon ….
 

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Good, the ISG develops a small (rust) hole in the diaphragm. This allows unmetered air to enter the manifold which leans out the choke Fuel to Air ratio on a cold engine — gives the rough stumble. As the motor heats up there is less effect but in time the hole gets larger and the problem gets much worse for a broader heat range. If you buy the aluminum block off plate from @XPRD that will be a permanent fix for this issue. Hope this is the problem and that you are able to fix it soon ….

Thank you so much ! Ya it is super rough now, I hope this solves it fingers crossed. Day one with my Mclaren today and it has a flat tire and that issue. And the tires are a week old. Hopefully just a leaking valve stem.
 
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RonMathMD
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