Double check all grounds

Remove them, clean, then reassemble including the one under the vehicle by the fire wall by your left foot area.
Test your alternator at the B+ battery post (the fat cable at the back of the Alt) Read volts with key on, engine at idle, 1500 and 2500 RPM steady for 15 secs. Does the volt reading fluctuate more than 1Volt?

Results: With key on you should get battery voltage. see chart above. You can NOT get an alternator to function properly with a bad or discharged battery.
If yes, bad regulator, brush contact to spinning parts. In other words, defective rebuilt unit.

Do a drop test on the battery cables in the trunk YES grounds and Bat + also. Many have chased problems only to discover the battery positive cable had been fired off by a hit. See positive cable view above.

Ok thanks I'll do my best with my little electrical knowledge.


For now I tried the drop test and saw no voltage at all
However in the configuration bellow the car refused to start i jiggled a little the negative multimeter side and the car made some weird noise and then I tried again and it started.

Disconnect your battery
Unbolt the jump point at the firewall
Clean both nuts and cable ends and reassemble

Ok I'll do tomorrow. I also noticed that when I put voltmeter on battery positive from the under the hood and other side either on the engine or negative jump point the voltage go all over the place. (Engine off)

Edit: now that I remember I already did that cleaning procedure it didn't work.

There is so much going wrong here, Why is your meter on A/C volts? A huge problem is that that people aren't familiar with their meters when things are working and then don't know what they are looking at when trying to trouble shoot compounded by often oxidized test leads that cheap meters come with.

Under "Things you can find on the internet"
Here is the manual for this handheld volt meter
https://asset.conrad.com/media10/add...ounts-4000.pdf

I have no electrical knowledge whatsoever. Even if I read the manual and understand it I still don't know what to set it I saw 2V when testing voltage drop.

Your best bet is still to take it back to the shop that did the alternator. They will probably have it figured out in a few minutes and charge you for an hour or two but you will be better off. Then when you have time you can study up on electrical and using the multimeter. There should be some electronics training kits available that can be really helpful with hands on practice instead of watching you-tube videos.

I don't know if it's related but when the engine is hot it sometimes get rough idle almost stalls specially when I decelerate to a red ligt. When cold it works perfectly. Today I tried to accelerate to max rpm in park for 15 seconds and after that it stalled and when starting it back again it also stalled. If I force it to run by pressing the gas pedal it stalls as soon as I stop. Also got a fireworks smell on the exhaust when I did that.

And multiple but rare times i started it and idle regime was very fast and oscillating rapidly clockwork between two regimes and was completely unresponsive to the gas pedal.
Can it be camshaft sensor or TPS or something?