HELP! 96 ZJ won't stay running!

[Ton_O_fun]

A friend of mine has a 96 ZJ with a 4.0L and all of a sudden the thing won't stay running unless your foot is on the gas. Its not throwing any engine codes or anything either...
It initially wouldnt start, but with quickstart came alive. Normally I would say fuel pump, but it will actually stay running with your foot on the gas, so that kind of negates that theory...

Any ideas??!!

 

[Twinkie]

My 'Runner acted like this one day after spending the day on Lingham powerline. Turns out it was water in the fuel *and* a number of vacuum leaks. As soon as we drained the gas and fixed the leaks, it ran like a top.
When it was acting up, once it was fired it would stay running if the motor was kept above 3000 RPM, made the drive home interesting!

 

[jlalonde]

I had the same problem with my 97 grand it turn out to be the fuel/air sensor . Mine has the 318 in it so it could be different .