yeah, renix model FI is about as advanced as a carb with electronic controls & knock sensor. takes a couple revolutions for it to hit and run. I'd place it on par with GM TBI systems. (being renix is batch fired fuel injectors, not much difference) it does use the oxygen sensor but it is definitely primitive by modern standards. DVOM is your best friend for a diagnostic tool. Later model (96+ for sure, perhaps 91-95 too) use STFT & LTFT. The 91-95 system is advanced for its age for sure, with minimally adaptive fuel tables, but not near as adaptive or readable as modern OBDII stuff.
@Jody Treadway knows more about the specifics of what each generation is capable of learning but WOT is still open loop. My professional guesstimation of the issue is still on IAC, TPS, or weak battery. introduce a vacuum leak and see if it will idle high. It ought to idle high, even if there is a valve problem or IAC with a good 1/8" vacuum leak, as long as the MAP sensor is able to pickup an accurate intake manifold vac reading. I suppose if the TB were gummed up badly enough from blowby that it would cause it not to idle. I have a good intake & exhaust manifold here off a good running '90 4.0 if you want it. Also just thought of that the Renix 4.0 used EGR. If the EGR were stuck open would also cause hard idle. swapping over to an OBDI 91-95 system is also possible to improve starting & run issues but involves changing intake & exhaust & down pipe due to manifold differences, but is supposed to net a gain of 15-25 hp & similar torque numbers. <discourse> All you need (ha, i hate when I hear that) would be the intake, exhaust, down pipe, flywheel, crank sensor, cam sensor/dist, engine bay wiring, speed sensor, cluster, ECM and patience to move a bunch of wires around on the bulkhead. I did the swap almost 10 years ago on an '88 but I changed the motor as well. My biggest beef with renix system was the long crank time. My thoughts were that if I have to spin the motor for 15-30 seconds to get it to start that if my battery were to be weak that I would get left stranded due to the cranking time(oh and I wanted the HO power). Of course on my swap I rewired the entire jeep bumper to bumper with the later model harness (dash, interior, wipers, everything, but you can slim down the new harness to On/Start/Fuel pump/Gauges/warning light wires and wire it up and it will be trouble free. That is what I am doing with my '87 YJ because I can't stand how carbs have a tendency to heat soak and flood, as well as angular issues climbing hills and side hills. (yeah yeah, maybe not with a high dollar carb but I'm cheap, and probably cost more going this route, but I want it the way I want it done, forget time and effort, it's a labor of love and if you cannot come to terms with that, well, fixing/upgrading/driving/wheeling older vehicles isn't a hobby/pastime for you)</discourse>
