Fuel pressure seems to drop

Does it die or stall out coming to a stop and after sitting for a minute or so it starts back up ?

yes exactly

Now usually the check engine light comes on when this happens but it did it to me with out the check engine light coming on the ( Torque Converter Solenoid ).Google this and it will tell you the symptoms of what happens to your vehicle when this part goes bad.

I have a manual transmission

Oh ok. Have this test done with a Exhaust System Back Pressure Kit. You can get this kit a mostly any parts store. It will let you know if your catalytic converter is clogged.

Not completely clogged but partially clogged that may be way it cuts of after driving 30 - 40 miles.

firebird338 is giving you very good information. Vapor Lock is an archaic term for engines with carburetors. Even the early Single -Port Fuel Injection systems in the late 80's maintained fuel pressure to injector and eliminated Vapor Lock

will try the catalytic converter, could one of the canisters that goes into the vacuum hoses cause this problem

Opps, I didn't see you have carburetor. Are you sure? Early Throttle bodies very much looked like a carb. Does it have a ECU at all?

Where is the catalytic converter at on a 1988 jeep wrangler and couldn't I just take it off and see if that fixes the problem?

no doesn't have an ECU, but yes it is a carb the engine is a 4.2 6 cylinder

the jeep seems like it is getting gas just stops after about 20 to 30 minutes like it is not getting the gas, usually can get it started again but then sometimes I can't

Opps, I didn't see you have carburetor. Are you sure? Early Throttle bodies very much looked like a carb. Does it have a ECU at all? Do you have 205, 4.0 or 4.2? Throttle Body SP Injection system was made by Renix and used from mid-1986-August 1990.

Ok I believe you, should have stayed out of this. firebird338 has a handle on it. Sorry for butting in with wrong information

no problem it is good you ask me these questions because I am not sure about any of this wanted to try everything I could though because my mechanic is tied up at the moment and can't get to me right away

Just Googled and typed in (Does a 1988 Jeep Wrangler have a carburetor) it took me to several sights but click on this one ( Fix idle and stalling problems on a jeep cj- 7 and early wrangler with 4.2 engines ) has step by step on how to fix problem.

Hey FordNut do not worry about it everyone's opinion is valuable I do not no everything I have taken some wrong information before also but it does not mean you do not no what you are talking about your answers and answered questions because they were on the money.

I have used some of your answers to answer some questions. Thanks

And also after reading my answer again ment to say I have given some some wrong information.

And that's a well and good, we learn from one another

And you that's right.

Thanks and I think both of you had good ideas, finally decided since I was a woman I may need help on this one so I took it a mechanic and hopefully he can figure it out, will let you know what he says. Thanks again!