92 buick century startup problem

Check compression. What was the fuel pressure spec, I'm an old psi guy. Check for applicable mil codes, you can those yourself.

3.5 bar is that around 50 psi? My info shows 41--47 psi, fuel pressure.

Hi. The compression is great. Fuel pump pressure 51,5 psi :) I hope it's not too powerfull ! Maybe fule pressure regulator is broken?
My skanner shows no codes :(
I just took off the MAF sensor and it's dirty. I hope the cleaning will help. If not, "I'll be back" :)

Usually with backfiring, you have to wonder about valve timing? Let us know what you find.

I've got an idea. Maybe it would be a crank sensor?

Ok. Finally the check engine shown a code 42 - direct ignition system fault or direct ignition system fault - bypass circuit open or shorted to ground or electronic spark timing circuit open or shorted to ground.
What should I do now? Is it because crank sensor is broken?

Is the crank sensor broken? At the moment, I don't know.

If the est or bypass circuit is open or shorted, that code will set. you can examine terminals A & B, both ends, plus wiring circuit. Do continuity test.

Ok. I checked all wires, and it seems to be right. Any other ideas? :)

From where I sit, I don't know what is causing it? I would have to look at it.

I hate to see you throw parts at it. The crank sensor is as good as any. You could check the sensor for ref voltage--ground and signal.

How about EST? Where can I find it and how to diagnose it?

I told you what the code means and gave you the wiring diagram. Engine cranking, do you have spark at the plugs? Also, use a noid light and check for injector pulse.