Cold explosions

Hello everyone in the forum. It is a pleasure to be here.
I need your help.
I just bought a 2008 Chevrolet, automatic 2.0 engine. The car only has 300 kilometers. In the morning when I turn on the car in cold, at the time it is heating, at minute a miniexplosions are heard, they last only 20 seconds and then disappear, if I turn off the car at that moment it is heard as a "rack", like a trrrr! strong. When the car reaches its normal temperature, stop making this failure. To happen again, the car has to stand for many hours. I must mention that driving the car even at its normal temperature and if the weather is very cold, it makes the mini -explosions constantly. The agency already changed the mofle, resonator and catalyst but the fault continues. They put the scanner, but did not throw anything. Please help me to know where to find the problem.
Receive a cordial greeting.

It may be due to ignition failures for having a spark plug or too open the electrodes of it.

I do not know how to tell you more with the data you give me but I suppose that if there is no code, there is no failure and if there is no registered fault to look it is a bit complicated.

That car is very possible that you carry Int ignition coils or even individual coils, (one by cylinder) so that the current losses from the high cables, at least they are very unlikely, not to say almost impossible. (Having defective high voltage cables or poorly placed on the spark plug cap caused the failures you mention in the engines a few years ago).

Greetings and while the car is in guarantee, although it is also a nuisance for you, give the can every time that is necessary until your car is in good condition.

Otherwise, the crazy people will be made and when the guarantee period is over, it will cost you time and money repair your car in conditions.

All the best.