hey new jeep owner here...I did a search on my issue but didn't come up with much in my year...
94 4.0 automatic 4x4, 175k miles, been sitting for 6 months or so... so I am getting the bugs worked out of it. I just bought it this week.
it seems to start hard, and I have to give it gas a little or floor it to get it to start like an old school carb... that shouldn't be the case on a 94 fuel injected engine im sure.
once it starts it idles a little low and sometime I have to pat the gas to keep it running...
now once its going down the road at 55-75 mph etc..it runs like a top, no miss, no issues...runs good and smooth. but when I come to a red light it almost dies or rough idle again... and if I go to a store park it, and when I come out its hard to start again...so doesn't matter if its cold or hot.

I have replaced fuel filter, run my first can of seafoam thru it, air filter, fixed a few vacuum leaks, hoses, etc... charged battery, changed oil, filter, and all this seems to make it a little better but still hard to start and idles a little rough.

could this be simply plugs? wires? they look like they have been replaced lately but who knows.
relay? fuel pump?
looking for things to try out..do...
I have noticed that when I turn the key in on position I do not hear anything, im assuming I need to hear a fuel pump buzzing? but I do nott...does nothing. does the relay control this? would it start if that was bad though?

thanks...
and I love my jeep so far!!

Probably best to start with all fresh tuneup hardware for a "new-to-you" vehicle. Assume nothing. I'd suggest Champion copper plugs gapped to .035 and premium wires, distributor cap and rotor.

By design, when you turn the key to the full ON position (not start), the fuel pump should energize and run for approximately 2 seconds. Have somebody else turn the key while you are at the back of your XJ listening; some pumps are pretty quiet.

Some basic fuel pressure testing would also be recommended. You can rent a fuel pressure gauge from many parts stores if you don't have access to one. For a 94, you need approximately 31 psi to start the engine and should stay there at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be sure that the vacuum line to the FPR is in good shape and is not wet with raw fuel, which would indicate a ruptured fuel pressure regulator.

Have your battery "load tested". Any parts store will do this for you for free. Load testing is absolutely, positively the only accurate way of testing battery condition. You can charge a marginal battery for days and if it isn't working properly under load, you're in trouble as the engine management system hates it when available battery voltage is low.

Good luck and keep us posted!

couple of question then...and thanks for your response.

1. where is this fuel pressure regulator at?
2. To do a "full load testing" on my battery does it have to be out of the vehicle and take it in somewhere or leave in vehicle?
3 could a low or weak battery or old battery cause my issues above?

also since this is technically my first tank of gas thru this thing... could it be just bad gas?
Plugs make it hard to start? although it runs smooth and nice on open road?

Auto zone can check it in the truck. Also might want to check the IAC. The valve might be a little gummed up.

where is fuel regulator?
iac?
relay?

Best bet is to get yourself a service manual if you are doing any work on your XJ. Haynes/Chiltons are widely available but pretty generic and have been found to contain an error or two. The factory service manual (FSM) is the most comprehensive for your exact vehicle. You can get a digital copy or ebay sometimes has hardcopies.

Here is a link to a digital service manual that you can download for $7.95

http://www.pacificcoastmanuals.com/j...e_manuals.html

pull the throttle body and clean it up. The IAC is the cylinder with the plug on the back of it. DO NOT PUSH ON THE PLUNGER, YOU WILL WRECK IT!!! Get a tooth brush and some TB cleaner, not carb cleaner, and gently scrub the tip. Then scrub the crap out of the bore and IAC slot

sounds good. i need to do that...
i installed new plugs today, (wow the ones in there were shot)...but still no change in idle or starting. once running down the road man it runs so good and smooth...nice.
I have read up on here about a check valve issue letting the gas drain back into the tank...hmm.. and also about the fuel pressure regulator vacuum leaks etc..

couple things i can hear the fuel pump now...but its only for a quick second and i mean quick second...but i do hear it.
i definitely have a vacuum issue somehwere because i only have air blowing out of the defrost area...no matter what its on, heat, air, etc.. would this be related? or two seperate issues?...

either way man i got some stuff to fix lol..
beginning to wonder buying a cheap beater good idea or not lol...hopefully it will pay off in the end.

They have to be. When there's a vacuum leak it makes the MAP sensor call for more gas to be shot into the cylinders, making it idle rich. If you pull the MAP tube out of the TB it chugs and sputters like it has an extreme cam in it, while stinking of gas at the same time. Pull the dash face and find out where that leak is. But still clean the TB thoroughly, it may need it anyways.

good deal. thanks for all your recommendations.. I will work on it tonight and report back. This site is a ball of information and making it fun to work on this jeep. Stressful but fun...as this is going to be my daily driver for awhile it needs to be rite...or I wouldn't be worrying about it to much.
so the list tonight will be...
clean the iac
clean the throttle body
recheck for vacuum leaks
find the fuel pressure regulator and check for leaks there
pull face of dash off and check for leaks there also.

Also pull the TCS and polish the probe until the brass bright. Actually solved my idle problem and removed codes 22(TCS) and 25(IAC).

ok I give...where is the fuel pressure regulator!!!???

At one end of the fuel rail which is on the intake manifold.

that's what I would think....
scratching my head....