1990 Jeep cherokee 4.0 sputters after it warms up. Runs good when cold. Changed plugs,wires,cap,rotor,air filter,checked vaccum lines. There are many sensors, what do I do next?

You need to do all the basic tune-up things: plugs, wires, cap and rotor, fuel and air filter.

This is because of the improper combustion, so you check the air filter, if the air filter is not good enough then the idling will go down and then the back firing will occur, in the same time check the Electronic ignition system for proper ignition cycle.

Try disconnecting the upstream O2 sensor(s). If the sputtering stops replace the O2 sensor(s). Mine was faulty and stuttering too and no check engine light or code was thrown. After unplugging the O2 sensor and monitoring for a week with no issue I had it replaced for $100 - $150 at a local shop.

Check for Vaccum Lost on avery hose Check PC's Valve, check hair filter, Vaccum hose system are important on any Vehicle for Idle control and air mixture calibration control for Fuel economie..

Check the fuel filter,and you may have some bad fuel with water and contaminates in it.Use some additives called lucas fuel treatment and heet a good fuel dryer.

COULD BE DIFFERENT THINGS BUT I RECOMEND TO HAVE IT CHECK WITH A GOOD SCANNER TO FIND OUT TROUBLE CODES BEFORE BEGIN SPENDING MONEY

Replace the fuel filter.

it sound like you have a problem in the air intake is there any air leaks there .

you can try useing a hot spark sloution,this is usualy an answe on gm products but its worth atry
unplug the ciol wire an leve it about 1/2 inch away its ******* the module but the system wil supply the spark

The 1987-90 Jeep Cherokee with the Renix Eletronic Engine controls take somewhere between 4-7 revolutions before the computer has enough information to get the engine started.

If it takes longe rthan that, it may be time for a full tune-up:
Distibutor Cap and rotor
Spark plugs
Spark Plug wires
Fuel filter
Air filter
and possibly an oxygen sensor