4.0 not running correctly

I have a 1988 XJ that starts some times and runs fine but other times I have to shot either into the intake to get it started but it doesn't always work. When it's acting up when it does start it sputters and backfires then once it's running it smoothes out but doesn't idle very long if I get it running and start to drive it the engine up and dies as I am going down the road after that it takes awhile to get it started again but once it starts to fire the sputtering and backfiring begins again it has the 4.0 I have replaced most all electrical componets. I haven't done anything with the injectors the fuel pump is running and has pressure the tank has 3/4 fuel. I just don't know where to look next any help would be appriceated

Give us a list of what parts you replaced and sensor or wiring tests you ran, from the battery to the sensors, etc.

My first thought for a 1988 Renix is a dying CPS sensor. It can be tested, with a good engine, good starter and good fully charged battery the cranking voltage must be above 0.50 volts (AC scale I think, read my old thread or Cruiser54 's threads and FAQ tips on the 87-90 Renix jeeps for this problem.

Common problems are dirty or loose or both, ground connections, bad connections at the battery post. Check the charged battery, should be 12.75 Volts, if not charge it up and try to start it. With it running the battery should read at least 13.75 (with AC and head lights on etc) to 14.5 volts with no loads.

The Renix jeep will not start reliably with out clean cables to the ground on the block and battery and the Positive cable at the battery and the starter. If they are not in peak shape the CPS does not produce enough voltage (cranking RPM is too low for the CPS to produce the needed 0.50 Volts) for the ECU to feed fuel and spark, and the CPS signal can come and go if weak and cause your issues. 70% of the time the issue is batteries and +/- cables....30% the CPS. Once running at idle the CPS will produce several volts.

Canking voltage at the battery must be at least 10.0 volts while cranking!!!! Weak battery, poor contacts can cause the voltage at the starter to go under 10.0 volts causing intermittent no starts....

If you replace the CPS the mounting holes must be modified....ask for details if you get that far.

Cool another Texas Red River chapter person!!!!! Welcome!!! You can to the right place. 8Mud, Cruiser54 me and about 4-5 other members here are hard core experts on fixing these Renix jeeps. I have 4 of them in Houston.

Almost forget, one other easy free fix that can cause you exact problem is a loose vacuum line from the throttle body base to the MAP sensor on the firewall!!!!!! It has a tendency to come loose enough at the Throttle body connection to look connected but leak enough to cause back fires and dying when you hit the gas peddle. Also once we get the first issues fixed, the TPS should be tested as it and damaged wiring to the one O2 sensor can cause back fires (TPS), misses at idle (O2 sensor only). But one thing at a time, lets get her running and check the voltages while running. Good luck, these are awesome hard to kill rigs if you learn the few tricks to debugging them.

How much fuel pressure?

And, when you get a chance, do Tips 1 through 5 at www.cruiser54.com.