I have a 1990 YJ 2.5. Here is what happened. My exhaust pipe worked it's way loose from the manifold. I drove it like this for a couple of days (out of necessity) before I parked it. About 3-4 days later, I went out and tightened up the bolts where the pipe goes into the manifold and now it won't start. It will start up for about 2 seconds and then die. After that, it will crank but won't start. If it sits for about 20 minutes, it will start for 2 seconds then die and won't start back up. There is also a PSSSSSSS noise after I turn the key off and the engine is stopping. I checked and there is spark at the distributor cap and at the spark plugs. I had a friend check the injector while I turned it over, and there is gas. Since it has been sitting I have: put in new plugs and wires, changed the fuel filter and put injector cleaner in. all to no avail. I am hoping that someone on here will be able to give me a place to check. Thanks in advance for your help.