hello, I am new to the forums. I am in need of some help on my jeep. I have a 1999 Jeep Grand Cherokee with the 4.0L. I replaced the transmission yesterday with a transmission from a 2004 Grand Cherokee. Before I started with the trans swap the vehicle was sitting for a couple months. The jeep ran really rough. The engine would start up with hesitation and would die when after i put it in gear and and stepped on the gas. That was before the swap. now the Jeep will not start up at all. When i installed the trans. the engine was not messed with. I replaced the crank sensor as they are prone to failure. The only thing left is the camshaft position sensor and the throttle position sensor that i will be replacing tomorrow. If anyone has had these issues before.. I could really use some help here. thanks in advance for reading my novel.

I have changed plugs, coils, fuel pump, and fuel filter.

Theres a 2 wire plug on the alt, unplug it and see if it starts. If it does then its your computer if not then good luck. The volt regulator is in the comp. My 2000 was doin the same thing and ran great when I would unplug the harness from the alt. If you have access to a battery tester then check your volts when running and when not. Also check the fule pump is cycling. Does it sound like it is firing like it wants to start?

first thing i would do is see if its getting any fire. if it is check the fuel pump and fuel filter. if those are good idk where else to go. hope this helps

Remember the Fire Triangle: Air, Fuel, Spark.
Verify each is available, one of them must be missing.
This assumes the mechanical timing of the engine is also correct.
Good Luck.

i replaced the crank pos sensor to make sure the air gap was correct...again.
i replaced the cam pos sensor seemed to help a little bit.
still no start.
the engine does not seem to be in time eventhough it ran when i pulled the tranny and now it doesnt. the truck backfires thru throttle body. still no clue on this.

yes it is getting spark and the fuel pump is cycling. i tried that and still no start so the comp is good. thank god!!!!

catalytic converter was glowing red hat after i got it started. new muffler and new catalytic converter. runs like a champ now thanks guys for the info.

The cat was probably full of liquid gasoline and had to burn off. It may have cooked your downstream 02 sensor. Check and see if the wires are melted.

Okay so I figured it was the cat and muffler. I was wrong when I cut off muffler and cat the vehicle ran okay so I figured that was the issue. This is not the case. The new cat I installed did same thing. I replaced The iav sensor and I am back to same problem except my catalytic converter doesn't glow red hot.
I am thinking either fuel pressure regulator or ecm.

Is there a relearn process for the cps tps or the iav?

If your budget will allow it, then an ODB2 scan tool would help the troubleshooting of sensors, also a meter to check resisitance and voltage levels on components. Don't forget to ring our the wires for continuity from the sensor to the PCM.
Back Fire and suspect timing: Turn the motor manually to TDC and verify the static timing is correct, including taking off the valve cover to observe the valves are in time. Good Luck with it.

well it sounds like a timing issue other than before i replaced the transmission it ran. the engine didnt run very well. the engine was hard starting but it did start so that rules out timing chain. i am going to replace the ecm in about 45 minutes ill post an update.

If you disconnect the neg terminal and unplug the computer harnesses for 1 hour it will reset the whole comp. Or you can disconnect the neg terminal but by doing the harnesses also it will do a master reset of it.

okay so i figured out the issue.... i purchased a used set of coils from the junk yard that were bad. i bought a new one and it runs great. now i have another problem. the vehicles trans over temp light is on and the overdrive will not work. just seems like one thing after another.