MALL240 wrote: ↑10 Apr 2020, 11:36 what I have noticed is that the idling is worse, it gives me jerks,

Check for air leaks on the intake side. Clean the Idle air valve.

i'll do. thanks A smoke test on the intake is the best way to find air leaks. Might as well smoke test the exhaust system and the EVAP system while you are at it. The are plenty of tutors on how to make a smoke machine. The simplest version is a plastic hose and a Cigar. You can buy one or have a s...

Replace Injectors as a set. Get the correct Bosch injectors that are remanufactured and flow matched. Sounds like the ignition switch is getting flaky but it could be a intermittent short in the wiring. The O2 sensors are probably getting pretty old but hold off on that. Have you smoke tested it for...

It is a 30 year old car. It going to take some finesse, elbow grease and pieces of eight to get it all sorted out.

As old as the car is, it is bound to have some air leaks which can be the source of the backfire. I suggest you smoke test the intake and exhaust system. Fix any leaks you find. Keep in mind a lot of .01s add up.

The unconnected cables most likely are options you do not have. Inspect them with a Loupe for scratches on the metal contacts.
Scratches = been used before. No scratches = never been used.

Got a Oscilloscope or or a Logic probe? Probe the signal on each injector.
If it was wiring I would expect misfires also.
A fresh set of remanufactured injectors is not a bad idea, US$50 - US$60 per set.

If it still has problems, check the air intake hose for cracks. Also check the idle air hoses for cracks and make sure all of the hoses are clamped down securely.

Maybe check the fuel lines under the hood to make sure they're not leaking.