I have a 98 jaguar xjr always ran great with no problems but I let it sit for about 2 and a half months tried to start it and it had a dead battery so I jumped it and it started fine for about 15 seconds then died. So I tried again and it starded but rough idles then dies after 30 seconds, I tried starting fluid and got it to start and run fine for about 15 seconds then rough idle at really low rpm but it dies after 10 seconds. Now it doesn't want to turn over hardly at all unless I use starting fluid.

 

I assume you mean "start without starting fluid"? Sounds like you have contaminated fuel, clogged fuel filter or bad fuel pump. Fuel goes bad rather quickly unless you use Sta-bil or similar product.
As for your battery, I highly recommend a battery tender, it will keep your battery fresh for as long as you need. My Vette sits for up to 6 months at a time and when I climb in, it fires up....and yes I use Sta-bil.

 

I ran some sea foam through it before the tank that sat in in for the 2 and a half months. Do you think it could be bad gas it's 93 from bp. Also I just replaced the fuel filter and still the exact same rough idle unless you use starting fluid

 

You need to get a code reader and report the codes here. But it sounds like you are not getting fuel, and pump failure may not result in a code.

Locate the schrader valve on the fuel rail, looks like a tire valve, may be on the left front hidden under other stuff. with the ignition o depress the valve and you should get a strong spurt of fuel. If not, think fuel pump.

 

The Schrader valve definately shot out pressurized gas out so the pumps are good I went to siphon out the gas and there was standing water in my gas cap area because the drain plug was plugged. Also inside of the gas cap it had a small amount of water so I drained the tank of fuel added new and some heet fuel treatment l. Still wouldn't run but it idled a little better with someone feathering the gas and me with my hand over the air intake. That would make it idle better but for only 1 min then die. My codes are P0175p1111p1336 p0112 p0102p0172

 

I also replaced the fuel filter

 

You can look those up...

Rich codes, IAT & MAF. Bad harness? Unplugged? Replace MAF/IAT? (Leave rich issues till those done as may be fixed in the process.)