Ok I pulled my 223k mile 4.0 in my 97 and tossed it a 104k mile out of 2000 explorer swapped over the different sensors.
I put in my cam synchronizer from the 97 I couldnt find a clear answer on how to put it in. I tried tdc and 26° atdc and it ran the exact same. And I did confirm it was on compression stroke both times

What happens is when I start it. She wants to die if I feather the throttle for a bit itll smooth out iacv kicks on it idles up settles down and runs perfect.

Now this happens every time I start it

Has new maf. Iat. Iacv. Confirmed tps is functioning.

This engine ran perfect when it was in the explorer.

Could my cam sensor be out of synch? Or is there something else that could cause this

I only have codes for evap and egr because I deleted those.

Any help would be greatly appreciated

 

Welcome to the forum

Unplug the cam sensor and see if it helps

Cold start on any gasoline engine requires engine to be Choked, that means Rich fuel mix and high idle until it warms up
Computer does that based on ECT(engine coolant temp) sensor, it tells computer the coolant temp, its a 5volt sensor near thermostat housing, dash board temp SENDER will be next to it, its 12volt, and usually has just 1 wire.

With key on the computer boots up and opens IAC Valve all the way for start up, does this with every boot up
So without touching the gas pedal, ALL fuel injected engines should REV to about 1,500 on start up, then RPMs will drop to "target idle"

Computer then looks at ECT sensor TEMP, to see if it needs to Choke the engine or if engine is already warmed up, ECT sensor decides idle RPM, target RPM, as well, computer has a "table" with temp and idle, i.e. 75deg = 1,100, 140deg = 850, 180deg = 625(manual trans)

So thats what cold start should be like

 

When I say it does it every time I start it I mean everytime. Even at operating temp I can shut it down for 2 seconds and it starts that way.

Also after it's running it can steadily hold any rpm with out falling on its face it will rev but refuses to hold a steady rpm.

I've never dealt with a cam sensor out of synch on one of these. Would one out if sync cause symptoms like that?

 

It shouldn't

Crank sensor is the main RPM sensor
They used just the crank sensors on most EFI engines for many years
Cam sensor was add for lower emissions and better MPG

Computer compares the two RPM sensors and will set a code if Cam sensor is not sync'ed with Crank sensor, crank sensor is always assumed to be correct

Out of time cam sensor can cause rough running on some engine, for sure, just never heard of that on the 4.0l OHV engines


Well.................... if you changed the whole engine and most sensors and still have the problem........................maybe its the computer
Do a sanity check on computer, unplug a few sensors and drive it until CEL comes on, get the codes