2000 SR5 Cranks but Won't Start

Hey guys, I'm hoping someone could help me out with a problem. This started a couple of months ago when the truck began topping out at around 70 mph. At this point it began to hesitate shifting gears, most noticeably taking off from a stop. I'm talking old ladies would be honking at me slow. On any kind of hill it would hit 55 mph max. I replaced the fuel pump and it ran perfectly for a week, no problems whatsoever. I used the old fuel screen because it didn't come with one, and the old still looked pretty clean, so did the inside of the tank. After about a week, it started to randomly lose power on the road and drop to about 10 mph, then fix itself (sometimes quickly and sometimes it took hours). It did this about 5 times on and off, then it got to where it would only rev up but not move. I ran some Seafoam through it, which helped a little but not much. The only other insight I can give is that it turned all the new spark plugs black within a month, but I've replaced them again. It's been sitting in my driveway ever since. I removed the battery to have it recharged, and when I put it back on it would crank over but not start. That's where I'm at now.

Things I've replaced; everything is OEM where I could find it:
New fuel pump.
New fuel injectors, all 6.
New fuel filter.
New plug wires.
New spark plugs.
New air filter.
New MAF sensor (was throwing a code for this but the new one didn't seem to change anything).
The O2 sensors on the exhaust were done last year.
Someone thought it might've been the catalytic converter because it was trying to backfire through the air filter box, so we removed the catalytic converter to test that but nothing changed.
The battery isn't great, but when the car was running it never went dead on me.

The only code I have stored is for a random cylinder misfire, I believe it is P0300. If I can get it to idle I'll search for new codes.

 

I forgot to mention that I cleaned the throttle body as well.

 

Which Engine do you have? So now it turns over but will not start now?

 

It's the 3.4L V6. And yeah, the engine turns over just fine but it doesn't want to start.

 

So what was the solution Cranks but want start I am having a serious headache with my 2002 4runner 3.4L V6 Cranks but won't start it set for a while so started at gas tank (drained and cleaned tank) added 5 gallons Super Unleaded, Seafoam, flushed line to inline filter, installed new inline filter, flushed gas line from inline filter until it goes into engine, replaced fuel injectors, put fuel pressure gauge on 50 something PSI fuel line, checked harnesses with bulb tester (they checked out), fuel injector rail has pressure, new fuel injectors, new spark plugs and gaps are to specs, new coil pack, checked for spark with spark tester (ok)( but I feel something is not talking right in the combustion process),cleaned throttle body , replaced throttle position sensor, replaced throttle intermotor, (my throttle body doesn't have the IAC valve I don't know why they have 2 different throttle bodies) new air filter, new mass airflow sensor, removed bolts from exhaust manifold before the cat ( thought it might be a stopped up Cat Converter), checked timing (ok), checked the cam position sensor, checked the crankshaft position sensor, checked my grounds. NO CODES other then Throttle Body Sensor Malfunction but I figured out that only when I take over the throttle control manually on start up holding the throttle body wide open it throws this code other then that NO CODES. SO HERE IS SOME HISTORY parked the car for alittle time battery died bought a new battery (installed a fresh fully charged battery) turned key on engine turns over with no foot on the pedal just turns over, push the pedal all the way to the floor car starts to spudder would run and spudder for 1 to 2 minutes at first now it want even do that but it still wants to fire (spudder for 5 to 15 seconds) but just want do it (start) at my wit's end here I have been in different forums for weeks now I see similar problems but I don't see solutions I pull a new spark plug out after cranking and cranking it seems to be flooding is it one of the following (ECM, VALVE NOT OPENING OR CLOSING, WIRING HARNESS (they looked okay to me) however the cam and crank sensors have a red and green (2wire harness) I thought I read somewhere in my weeks of reading that they have to have continues 12V I have nothing no 12V just figured this out) the little 3.4 acts like it really wants to start but II just fell like something is just not talking HELPPPPPPP!!!! Oh and I have taken it to a couple of mechanics and the were charging for every little trace it got really expensive quick when I can trace myself I felt they didn't know exactly either they were guesstimating Thanks for any HELPPPPPPP! Will

 

Well figured it out parked the car for too long all the oil settled did a compression test on cylinders on passenger side front 2 cylinders had No compression and No compression on front 2 cylinders on driver's side took valve covers off too see the lifters were stuck exhaust valves were open so the engine would not combust alot of carbon build up so I sprayed B12 carb cleaner around lifters and sprayed penetrating oil (PB Buster) and Marvel mystery oil around lifters for 2 days morning and night took a wooden stick and teflon hammer and gently tapped around the stuck area while another person was turning the motor back and forth from underneath and bam they came unstuck and the engine started right up without taking the heads off and having a major job on my hands