I have replaced plugs, wires, cap, rotor, new optima battery, coolant temp sensor, i even put a new fuel pump and filter assembly in. i have spark and pressure at the fuel rail is 40-43psi. the cherokee was just having trouble cold starting but now it just trys and sputters won't start!? iam very frustrated cause i love this thing! what could it be?? possibly the brain? map sensor? and its not the CPS because it does try to sputter when starting so it is firing. sometimes almost fires then just sputters out

 

Was it doing this prior to you replacing all those parts?

 

Could be crank shaft positioning sencer. It did that on mine. About 40$ at O'Rileys. You can also read the codes without a scaner or taking it anywhere. Heres how. Start by turning the ignition key to the last stop before it starts,( on,off-on,off-on and leave it ) 3 times, leaving it on, on the 3rd time within 5 sec. Some models you have to do it 4 times, leaving on, on the 4th time. Ok I just did mine, its 3 times. Make sure to start with its is showing your mileage. get a piece of paper to write them down. if all u get is 55, that means it not putting any codes out. U should be able to fine a list of all the codes and what they mean on the internet or on the forum. I cant remember where I found them but I just printed them out when I did find them. If u cant find them tell me what they are and I'll get back with u.