Hi. I initially do not suspect piston slap, but somebody commented in YouTube in my video that these cars always does piston slap.
My main suspicious is a mix of belt/pulleys and lifter sound at the start.
My mechanic skills are very limited. Lets see if i can have the car checked by a professional mechanic soon.

 

Ok, would be interesting to hear what the mechanic thinks. Be sure to take it to one that's known to be familiar with your Neon engine, so you get a reliable diagnosis.

 

Hi again.
I have a mix of the common piston slap in cold start and alternator or service belt noise.
I have found in internet a lot of people reporting this piston slap noise when the car starts in cold wheather. Some people suffering it soon after being done an engine rebuilt, some people suffering it with engines with low mileage... so it seems that there is not known fix for it.
Some people think that with a thicker oil such 10W40 or 15W40 sometimes you can mitigate it. I might test in the next oil change.
I am now wearing a filter with anti-return valve and 0W30 oil and the noise persists, or even i'd say it is worse than with 10W30.

 

If its piston slap, it usually goes away after the engine warms a little. For some vehicle manufacturers the piston slap problem came about after they shortened up the piston skirts to lower sliding friction, to improve engine efficiency & that caused the cold pistons to wobble side to side in the bore as the piston connecting rod changed direction at the top of its stroke on a cold start, until things warmed up & expanded some so the piston fit tighter in the bore.

If the 0W cold temp viscosity is lower than the viscosity of the 10W at the same starting temperature, it might make it a little louder. Piston slap is not thought to cause a engine longevity problem.