1994 Sidekick 16v AT 4x4 4dr virgin ECM Ruby's still there

[fixkick]

great questions.
the 4 injectors are about 10ohm coils (varies by engine temperatures) if all 4 read the same then they are good coils.
the injectors, are modulated. PWM (to keep them cool when energized)
the ECU is just a tiny slow computer, and embedded processor.  with firmware inside called  ROM. (can not be changed this rom only ECU full)
The injector pulses are based on many factors, and all engine modes.  cranked, cold running , hot running, idle, cruise and wot, (and accerlation)
the factors effected all ECUs and computers are the inputs, just those.
all the top sensors are.
lets do hot running, idle
#1 fuel pressure at spec, at idle. is #1  (& no leaking injectors, yours passed this test leak down , 1minute test)

1. MAF air flow (mass air flows) injections match this. flow, 14.7 to 1 ratio called Stoich AFR air fuel ratio mix.
   
2. ECT , shows 300  ohms for 180f and steady all the time hot.
   
3. IAT, only does very little adjustments to fuel, some 1992 G16 have none at all.
   
4. O2,  the OS find tunes all errors out of MAF air flow,  for 14.7 :1 AFR, at idle and cruise hot, (steady foot)  heater must work !
   
5. TPS only has 1vdc on output at idle and does not effect AFR until driver makes this voltage go high real fast. (called acceleration to 12:1 AFR rich)
   
6. The ECU must not be in limphome mode (failsafe) or goes super rich, and spark advance dead, and no idle controls. 12 code means you are not here.
   

the o2 heater must be good, some early ECU do not report the heater dead when it is dead,  1amps of current flow about. at 12vdc.


one top injector show says (witchhunter)
We are starting to see quite a few Chinese made injectors that are junk, most have the factory part number and not the correct logo. Be careful when purchasing so-called, new injectors for a very low cost.
(never buy ebay injectors, or get junk easy for sure china direct crap)
in fact have you real stock injectors PRO cleaned is far far better, $23 each , using reverse Ultrasonic cleaned (10micro screens inside yah)

the crack that loves to happen is here (loves to crack here#4 rear) only on 16valve engine, never 8v.
this crack is super bad, due to works one minute , not next , repeats as the metal heat up or cools, under varying engine load, the crack sucks in air that is 20% oxygen (02) and causes the 02 sensor to read crazy wrong, (near 0 volts wrong !!!) and goes RICH when it does. on 1995 and older super rich.




one more mode. called EFI getting lost mode. (not documented any where,)
the ECU hot, wants to pull injectors to STOICH at idle, it prime goal is this, and EPA and Calif ARB0)\
called closed loop mode.

to do that magic the ECU loops on the O2, it reads the O2  about 6 times a second (that is why the o2 CEL makes wave form slow)
this loop causes the 02 to hunt (ecu is the hunter) and works hard to pull, the fuel to center of 02 range about 0.45v (.5v for short)
this is why all shop check the o2 output super careful now, using scope or in OBD2 the 02 scan live mode of the tool.
the 02 can be wrong many ways, stuck high , stuck low or offset or correct. (centered and fast wave)

obd2, o2 scans, see the O2 swing at hot idle"? it must and not be offset, it is correct here. or use a real scope on the OD Cel + and minus wire pins)


The o2 is hot tiny battery, called CEL. acts like 0 to 1vdc battery, per BOSCH web site on top, the wave above is ECU hunting STOICH. (perfect AFR)
sadly tech1, can not do that. only 1996 and up newer cars USA, can. or outside USA even 2004 year up, we have list of world compliant cars. to OBD2.

Sadly#2 I do not have 16valve injector pulse-width data hot idle. (my bad for forgetting to do that with my shop scope or oBD2)