Ωhm

You'll know. Fuel drops in the hose. Should be wet.

Looks like your ride had A/C. Nice.

Make sure no fuel is in the fuel pressure regulator vacuum line. Leaky diaphragm.

Yea, from that side view shot, looks upside down. Check out other photo's, you'll see.

Look into your front grille. ↑↓ Make sure it's installed properly. Welcome to CC.

Somebody give me a cheeseburger.

RENIX 4.0L has no Closed Throttle (CT) switch unlike the 2.5L which does. This CT value is learned over time (40 or more key starts). I know TPS is set to ≈17% at CT, but that’s just a starting point. I’m with you, hope this does it for you. Take it.

Keep in mind when EGR solenoid is ON no vacuum is allowed to flow and the EGR valve is OFF.

EGR should have nothing to do with engine idle. I wonder if given time and EGR connected, could ECU learn its way out of this problem. You've done a lot.

Good to see INJ PW ≈5.4ms at idle with warm engine. Idle RPM’s still seems to be hunting (up/down) for smooth idle of ≈750RPM’s. Few things to think about: -slow to respond IAC. REM can show you what it wants the ECU to do, but is IAC moving quickly enough? -slow to respond O2S. LEAN/RICH should switch just short of the speed of light. -leaky/faulty injector(s). When ST drops to 90, ECU will take fuel away. ECU thinks RICH. -try a known good ECU, if possible. I know haha. Looks like you can leave EGR connected unless you can say, yes EGR is the problem.

Before that happens, at idle, can you post up INJ PW and fuel trim values, both ST & LT. Thanks

If 2.5L learned anything from the 4.0L, both being RENIX, I would hope it would be the TPS & MAP way of how to do fuel strategy. 2.5L still had ISA, with build-in Closed Throttle (CT) Switch. 4.0L learned CT.

87 vs 88 electrical manual wise, show ECU pin C200_8 as WOT(87) or PSPS(88). WOT needed to add fuel while PSPS needed to kick idle up (used when in parking lots to prevent stalling). IIRC

You need to determine if your vehicle has a WOT Switch or PSPS Switch?

All photos look good. You didn't jump a tooth or two. Indexing is not your problem.

Good video. One man show with him.

Plug removed, thumb over the hole, only tells you when that cylinder is on the compression stoke. Time to fire (ECU) the plug (distributor) for that cylinder.

Yea. Plugging the hole and rotating the engine needs two people. Let see if I can make this even more confusing. Instead of Cyl#1 plug, remove Cyl#4's plug (easier to get to). Then the next time the timing mark shows up, you're on TDC compression stroke Cyl#1.

That timing mark on the crank (0°) can show up on either TDC for Cyl#1 or Cyl#6, depends on where the camshaft (valvetrain timing) is. Need to determine which one. Tip 12 tells how to do that.

Is this the tip 12 you're talking about? Tip 12

No, if your timing was off, it would be the fault of the ECU or ECU inputs. Timing is controlled by the ECU. Indexing is where the tip of the rotor is in relation to the distributor tower terminal. Crossfire, weak spark are some of the symptoms. Try and determine if your setup (index) is like that as shown in the photos. No need to cut tabs or remove distributor. Just check indexing.

Distributor could have jump a gear on the camshaft.