hi im adam

I got a 96 xj... wont idle without assistance.

it will start and stay around 250 rpms and dies soon after.

40 psi on the fuel rail.

I didn't have a gasket on the throttle body, but that didn't fix anything




Any ideas? on monday its going to a friends shop if i cant get it by than

tjwalker

1. 96 is kind of a hybrid year for the fuel pump circuit. But I'm pretty sure that it is supposed to have 49 psi at the fuel rail. Plus or minus 5 psi. I'd verify this if I were you, because if that is the case, you have a fuel pump problem! The low spec would be 44 psi.

2. A common cause is a marginal battery. And yes, you can have a battery strong enough to start the engine, but marginal enough to give the engine management system fits. I answer a couple of threads a week that turn out to be this. Have your battery LOAD TESTED at any parts store (free) to be sure.

3. Dirty throttle body and idle air control. Clean them BOTH

4. A bad throttle position sensor.

Bigclubs

250 rpm sound very low, I remember most vehicles should run in the 750-1000 rpm range.
I do not have that problem on my XJ, but my 91 sunbird convertable (195k)would die at intersections while at idle without added peddle assistance. Looked online for months about stalling and there are also a recent post here about XJ idling problems.
I just replaced my IACV (idle air control valve) on the convertable today and now it doesn't stall. Hope it will keep running, haven't run it enough to see the results.
There is a post recently telling about cleaning the IACV on the inline 6.0l motor. My cherokee has 145,000 and I should look into cleaning my iacv also. The iacv should have (2) #25 torx screws holding it in place behind the throddle body, remove the motor, reconnect the wiring, while turning key to the ON position without starting the engine, the plunger should move IN or OUT. This would tell you if the iacv motor is working properly. My iacv did not move at all, so I replaced it.
Look under the post "Would you buy a 99 4x4 140K?" TJWALKER explains how to clean the IACV.

Potatowalker

https://www.cherokeeforum.com/f2/col...rm-fine-83014/
TJ has some awesome advice!

I've got a new fuel pump assembly to install. I can get it to start and run fine most of the time by doing the "poor man's prime" but there are mornings where it doesn't want to start even with good fuel pressure. When this happens it sounds just like your problem. I'm pretty sure it's my IAC or TPS. I've cleaned the IAC but that doesn't mean it's still actuating when it should. Gonna put the fuel pump dealie in here in a few days, then with the low psi issue gone I can find anything else that might have gone bad a little easier.

Get a fuel pressure test kit and a multimeter if you want to figure it out yourself. Pretty inexpensive, handy to have around, and easy enough to use. That's what I did, and I'm making good progress... so far... will update my thread when I find the solution(s).

Good luck!