Cold rough idle issue.

[prerunner1982]

97 XJ with 4.0 and about 150K miles.

Hard to start and once started you have to feather the throttle to keep it running. Once warmed up starts and idles fine. Let it cool and it's hard to start and keep running again.

The IAC has been cleaned which allowed it to idle better when warm.
Coil and distributor cap/rotor have been changed as well.

We (Father and I) are thinking it may be fuel related. The previous owner replaced the fuel pump/sending unit and likely didn't get the seal on right as it will over flow from the top of the tank. Could this leak and lack of pressure in the tank have anything to do with the idle issue?

Any other ideas?

Thanks

[4.3LXJ]

I think to answer that you need to check your fuel pressure. Got access to a gauge?

[prerunner1982]

Yes and that was likely going to be our next step, but wanted to see what others thought as well.

[Mudderoy]

My fuel pressure would drop to almost zero about 15 seconds after I turned off the engine. On first start up it would run rough for about 30 seconds, maybe. I replaced the submerged fuel assembly and all the problems went away.