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Discussion Starter #1
Hello i am new to the forum, live in sweden.
I have problems with an CTS-V 2009 with 50000km/32kmiles.

The car have some misfire att full throttle at around 200km/h/120mph and high rev, and then it will send P0300 random misfire. sometimes i get P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem.

spark plugs and wires are replaced, cant find any vacuum leak.

No tune or mods.

i can send a log from i HPtuner if so.

sorry for my bad English.

Regards M
 

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Check connections to the coil packs. Provided you know the plugs and wires are good, problems at high RPM are going to be caused by problems with power. The motor vibration increases with RPM. Something's not fully connected, as the vibration increases the connection can become intermittent. I had an ignition problem on my 02Z06 (18 years ago) that only happened at high RPM. There was a cable that was routed around the back corner of the Head, and the corner was machined surfaces, so there was a relatively sharp corner. When the motor vibrated, the cable vibrated and tapped against that sharp corner. Over time, it chopped away at the insulation and exposed the conductor, and from that point on when the motor vibration got big enough I'd get misfires from that wire shorting against the Block.
 

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I recently had a misfire problem. The codes said that #7 was misfiring. The car barely ran. I tried changing the wires and switching the coils. Nothing. I gave up and had It towed to my mechanic. They finally figured out that one of my cats had collapsed cat that was completely clogged. Good luck.
 

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Discussion Starter #4
The car goes well until around 120 mhp. can't find any fault on the cables

Regards Mattias
 

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The car goes well until around 120 mhp. can't find any fault on the cables

Regards Mattias
I'm sure you have tried this already, but maybe swap the suspect coil pack (if any) with one on another cylinder, and see if the misfire follows to that cylinder. If not, then I would move down to the cat's. I wouldn't think you would have a plugged up cat at that kind of mileage, but anything is possible.
 

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Fwiw, and I am baffled as to why, but my plug gaps widened and caused misfires under load.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #8
how reliable is the charge gauge in the car? It looks like it is very high and wants to think it is when it misfires.
 

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Discussion Starter #10
Hello again, i have done some comp test,
bank 1 125, 140, 145, 145.
bank 2 130, 140, 125, 140.
Cold Engine and full throttle.

if i add som oil in the 125 cyl it will goes up to 145.

I have found out that the car has been very tuned before, the engine crashed and was replaced. But I start to doubt that it was really changed.
 
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