99 Cherokee Problems..please give me some ideas

I have a 99 Cherokee Classic that has some problems. When it is started it will idle fine, then suddenly the rpms will drop and it will run rough for a few seconds. It then catches itself, and returns to regular rpms, but when you start down the road it will suddenly start bucking, and jerking like its not getting any fuel. I have fuel pressure, and ive replaced Idle Air Sensor, Crank Sensor, and Throttle Positioning Sensor, and it still hasnt fixed the problem. Does anyone have any ideas about what is wrong with my jeep??

What about the fuel filter, spark plugs, plug wires, ignition coil, and distributor have you checked them yet?

Try plugs if you haven't yet. At least look to see if they are fouled and check the gap.
Test the battery and ground (very important). Test the coolant temp sensor.
You can do a fuel pressure test like another threads says and tape the gage to the windshield.
You can't change fuel filter unless you take out the fuel tank because it is inside on the fuel pump module.

I have just replaced the spark plugs, plug wires, and distributor. There is plenty of fuel pressure to the fuel rail. My mech. and the jeep dealer in town can't figure it out. It is not throwing any codes. Runs fine at startup for 15 sec. then it starts cutting out for 30 sec. then runs fine until I shut it off for 20 min. Then at startup it does the same thing. I will check into the coolant temp sensor.

Sorry to hear that...

Sounds like it might be related to the emission control warm up system...

Can you have the Jeep dealer or someone else do a substitue swap of a PCM (Powertrain Control Module) on it to see if that is your problem?

That is what we use to do at the dealership.

Do you have extended warranty or such?

Is the powertrain control module expensive? I have no extended warrenty.

I don't know and I would hesistate to tell you to get one with out testing. You need to find a reliable dealer with a tech that knows that model. I can get you a wiring diagram, but that can't test the computer. PM me and give me your email if you want a diagram.

The thinking I have is that when the engine starts, the computer retards the ignition and does some other things for the first 30 seconds to quickly warm up the emisson control and the cats(the catalytic converter). Unfortunately, I don't have the emissions manual.

Try to disconnect the O2 sensor and maybe the coolant temp sensor to see if it will trigger the "safe" mode. With something that consistent, you can try and isolate it down to the system first. BTW, do you like in a big city? Try a different dealer. Call the Daimler-Chrysler zone rep. (factory).

Second thought, maybe we should revist the fuel pump inside of tank issue also. Disconnect the line (depressurize first) and take a one quart sample.
Make sure you have volume and no contamination such as water.

On a final note:
https://techauthority.gltghosting.com/webapp/wcs/stores/servlet/CustomerHome?langId=-1&storeId=10051&catalogId=10051
The above link is the the D-C factory tech information site.

Anyone else with idea??

Check the timing...may be a little off. Had a VW that did the same thing.

Did anything happen before this? Could be a bent valve or one that sticks once the motor heats up. My dad has a Cub Cadet that suffered this problem.

Unfortunately, the owner hasn't replyed to what has happened here, but the timing is not adjustable here, although he said he replaced the distributor. I would take a second look at the ground strap at the middle of the top back of the firewall (which I noticed on mine yesterday) and clean it.