[GottaCruise]

"or something else hindering the fuel supply."

If introducing fuel shows improvement, and you haven't changed it already, the Fuel Filter would be a logical first step.

 

[GottaCruise]

Another sanity check, disconnect the front Intake Tube from the airbox - open that intake port up on the airbox to confirm intake side is breathing well.

+1 for confirming spark plugs and wiring, cyl. 1 is at front of engine, 4 is at back firewall, (2) coil packs:

Coil pack "a" - Short boot on plug 4, wire to plug 1,

Coil pack "b" - Short boot on plug 2, wire to plug 3.

On original OEM coil packs, there s/b (2) resistors in-line between the short boot and the bottom coil, to balance out ohm load. Valid range for the resistor(s) is 4.9k - 5.1k Ohms.

--
Check the Engine Coolant Temp. sensor wiring, and connector - this plays a big role in determining timing / fuel injection. That's the (2) wire sensor connector to the right on the thermostat block, facing front of vehicle.

 

[GottaCruise]

Rewinding a few years,

Have you checked compression?

When was the last timing belt service? Has the belt been checked / timing marks verified ?

Have you checked the Ignition Coil Pack (CP) pigtail lead from the engine harness -> to the CP connectors to ensure they are on securely .. (not cracked, brittle, or wiring frayed),

Have you checked the ignition wires, and short HT leads and plugs for any issues (oil, carbon tracking inside boot, failed HT Resistor inside the HT lead, if original wires) ?

Have you pulled plugs, verified condition, verified they are the correct plugs for the vehicle, and checked plug gap?

If fuel is good, air intake is clear, exhaust is clear - then ignition, mechanical timing (belt/crankshaft keyway), engine compression, or a sensor related to mechanical timing (Cam Sensor, or improperly installed Crank Sensor) are items that come to mind here that I would check.

*** Sanity check: verify good voltage to fuel injectors, Ignition Coil Packs, Fuel Pump, and ECM - low voltage / poor grounds will cause many 'gremlin' issues: make sure all components are getting good voltage ( Battery B+ voltage, within .5 volts of direct battery reading. ) ***


Edit: The fuel pressure readings you posted (50 cranking, 40 running) are spot-on. Unless the fuel filter is original / badly plugged, I don't think fuel pressure is the issue. Check the regulator vacuum line, just to be sure it's in good condition and on securely.



Regards,
GottaCruise

 

[GottaCruise]

Yes compression is fine


New belt, marks verified


All look fine

All good


The only item listed that hasn't been replaced is the cam sensor and I have one on the way.



I haven't checked all that - but I have verified the ground between the engine and chassis is good.
The only one of these items that you listed as a possibility that still makes sense to me is the voltage at the injectors. How do I check that? Or more specifically WHEN? Do I put the meter on them and make sure I'm getting 12 volts while someone is cranking it over? To me the coil packs theory doesn't seem to fit the symptoms. Either they fire or they don't, right? In this case they do. It just won't rev up above 500 RPMs or so.


Filter is new, so is the regulator, vacuum hose to regulator is fine.

The weird part is that when it does sort of start it idles slowly and will not rev. Sometimes when it won't start, pulling the fuel pump relay out of its socket will get it to start. But it still only idles a really low RPMs and still no throttle response.

I've about come to the conclusion that the problem pretty much has to be the ECU. I'm thinking it is fried. I've replaced just about everything else. Here is the list of new components.
Spark Plugs
MAF
IAC
TPS
Timing Belt
CPS (Crank)
Fuel Pump Relay
Fuel Filter
EGI Relay

About the only things that haven't been replaced that I can think of are the cam sensor and the ECU.

Fuel Injectors: electrical: test with a DVOM on positive for 12v line, operation: NOID light test

https://www.amazon.com/OTC-3054E-Noid-Lite-Test/dp/B0071JJYLO

mechanical - pull each injector, and run a volume test.


Ignition: true, unless a CP is cracked / damaged / bleeding voltage to ground through a crack, or carbon trace.
But yours is running so poorly / dying on any kind of acceleration, that I would focus on other causes - since you have verified condition of components, plug gap, and firing order.


Timing: I would verify the crankshaft snout key-way, if here.. (And check engine vacuum.)

You have to pull everything off to -visually verify-, that's the only way to be sure.

http://www.kia-forums.com/1g-1993-2002-sportage/75482-broke-then-good-then-broke-again-6.html


Cam Sensor: anything's possible, but if it's running .. With absence of any DTC code indicating an ECM <-> Cam Sensor communication issue, would be suspect only after verifying crank snout, and mechanical timing.

==

Don't want to point you down a wrong path..

You are on the ground there (so to speak) - testing & verifying condition of components is needed / and common sense is best.

If here, I would hookup an old school vacuum gauge and observe reading: if low, would suspect Crankshaft snout key-way issue / failure..

I would run another compression test, record readings: if all are uniform (within 10 psi of each other) but universally low, again, would suspect Crankshaft snout key-way or incorrect Cam/Crank mechanical timing,

Posts #18 & 19 above in this thread ..

** If above are good, voltage to ECM (+) line is good / within .5 volt of Battery (B+) voltage, only THEN would I suspect a bad ECM. But again, you know condition best, "Common Sense" applies.


Hope this helps,
GottaCruise