I bought this 96 Jeep xj that sat for months. We jumped it to get it started and let it run parked for about 45 minutes. I went to drive it home and it had very little power. I drove it about three miles where I parked it and had it towed to a close mechanic. They said the cat was plugged and sucked everything out of it but never could get it running so it was dropped off at my house. Since then I have checked for spark at the coil grounding it off the block with a new plug. I have spark. I rented a fuel pressure test kit and I have around 40psi and it holds. The motor will run off starting fluid but any touch of the pedal it stumbles and dies. I put a new battery and terminals on because old battery was shot. New plugs wires and cap. The plugs, after getting it running the first time were all black and sooted. Once I cleaned them and got the jeep started a second time I pulled them a second time and same result. Before the new battery I had three codes
24 tps
21 Code 21-Upstream oxygen sensor response slower than minimum required switching frequency. Upstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor heating element circuit malfunction. Downstream oxygen sensor input voltage maintained above the normal operating range.
51 51: Oxygen sensor output indicates lean too long.

the 02 sensor downstream is disconnected. I am stumped any help is appreciated.

 

the rear O2 sensor doesnt matter

front O2 sensor and TPS matter a lot...I would suspect those 2 items

tests can be done using live Data OBD2 reader

 

Would a faulty tps cause a crank no start but still start with starting fluid?

 

Any time you have a cranky o2 sensor....disconnect it. It will set a code but the computer now goes to a standard preset fuel scheduling. Its not the most efficient but the engine will run "well" on this schedule. your 96 may or may not have the fuel regulator on the rail...if it does pull off the vacuum line and make sure there is no fuel on that side of the regulator. Also your thermostat temp sender may feed the gauge or there is a separate sender for the gauge...if separate then put a ohmmeter on the thermostat sender when cold....should read very high. Cold = high resistance. Warm or hot is much lower resistance. A cool signal enriches the mixture. A warm or hot signal leans out the mixture if your gauge is driven from the other sender you would never know what the tstat sender is doing

 

Does the 96 have the MAP up on the firewall? If so make sure it's line is connected and flawless.