Bad Stalling problems

My sons xj is an 89 4,0 auto, 231. About 2 months ago it started having a stalling problem just when he started to take off. Well recently it has started to stall all the time, when you press the throttle, when you let it idle at a stop sign, just plain constantly. It will always start right back up again but it has got to a point where it is dangerous because it will stall at low speeds and he loses his pwer steering and brakes.
We have replaced the CPS about two months ago and checked the TPS and it is within spec. Any help would be great,because I am at a lose so that means its time to pay a real mechcanic :rattle:

Thanx Digger

Have you checked the EGR valve?

No , Didn't think about that one.

hey test the pressure at the fuel rail and get back to me. its a little thing that looks like a stem from a bicycle tire. it should read i believe 30 then pull the vacume line of the fuel pressure regulator and it should read 39. sounds like a fuel problem. if it starts right back up it cant be electrical. just dosnt happen that way. also when he drives it next have him keep it in a lower gear for a little bit. like 3 or lower and keep the rpm's mid range. if the fuel pressure checks out. and it runs good in a lower gear. it might not be lack of fuel but to much. i had the same problem when my starter relay went out. it has the power for the pump after the ballist. it kept the darn fuel pump running at full speed all the time and would flood the engine out at low rpm's. but because of the over abundance of fuel . it always started up like it was new. right after it died.

One thing my son failed to tell me until tonight, It usually doesn't start stalling untilthe motor gets warm.

The EGR solenoid isn´t supposed to activate until the motor warms up. Plug up the vacuum line for the EGR. Don´t know if the 89 has the transducer or not, but if it does, plug the line before the transducer. Take it for a test drive. Don´t leave the EGR solenoid unplugged, the default is open, and it will suck vacuum. Better to plug the line down by the egr or put some kind of plug/cap on the EGR solenoid.

I had a simlar problem at low RPMs and it turned out to be a split vacuum line going to the MAP sensor on the firewall. As said earlier, the EGR valve is another suspect.

Takin a WAG here,fuel filter??