1999 XJ 4.0L Stalls after start

Guys, I know there are quite a few threads dealing with stalling issues, but I haven't found one that will help me.
Vehicle Stats: 1999 XJ Classic, Bone Stock, 140,000 Miles. 4.0L

About 3 months ago, I started my jeep and it roared to life then immediately died. I tried it again, and each time it would turn over, run for 1-2 seconds, then the rpms would drop and it would stall. It would run if i drove with 2 feet (right foot feeding constant gas to keep it above 500 rpm) but the second i took my foot of the gas it would die again. The other jeep forum made me think it was my crank position sensor, so I swapped that out. It ran ok for about 3 months, then this saturday it started doing the same thing again. I tried unplugging, then reconnecting the CPS again and it ran ok, then died again the next time i tried to start it.

Any ideas?

Again, simplified version: It will start, then almost immediately die. When it runs, it runs fine.

Have NEW(ish, like in the last 6 months) spark wires, plugs, distributor cap, rotor, battery. The issues began separately from replacing these parts.

Thanks for the help and tips in advance.

Seems to be a rash of this going around.

As you can FORCE it to keep running by keeping the RPMs up let us A**ume that it isn't the crank sensor/PCM/ASD relay/Fuel pump relay.

Try unplugging the IAC--idle air controller--on the throttle body then start it and report up what result you get.

I would do two things out of the gate:

1. Confirm proper fuel delivery with a fuel pressure gauge. With a 99, you are looking for 49.2 psi, plus or minus 5 psi. Proper fuel delivery must be ruled in or out early in the troubleshooting process.

2. If fuel pressure checks out, TEST the throttle position sensor. You will need a manual and a meter (analog meter best) to do this.

Good luck and let us know what you find!

My 99 4.0l bone stock did the same thing, try cleaning the idle air control valve and if that doest fix it just buy a new one. They for some reason get stuck shut and starves the engine of air when you start it and then after holding down the gas it slowly and it will start to work normally. And sometimes it wont do it i would imagine.

so get some throttle body cleaner spray the heck out of that thing, and see if that fixes it. If not get a new one from napa.

I would definitely check the TPS. Disconnect, then reconnect. If problem persists, check voltage and/or replace it anyways. Also, Confirm that the alternator is putting out 14v to the battery, even though your battery might not be dead you might as well check and make sure its not a charging issue.

Since you posted that you can drive the Jeep with your foot holding 500 RPMs verifies the TPS, both CPSs and fuel relay are working.


X3 on the Idle Air Controller

CharlesS said:

Since you posted that you can drive the Jeep with your foot holding 500 RPMs verifies the TPS, both CPSs and fuel relay are working.


X3 on the Idle Air Controller

Click to expand...

Not necessarily.. since the tps or cps may not be getting enough power. When you raise the rpms, more amps come from the alternator...

But yes, IAC is possible but has already been mentioned. New ideas should be welcomed. Just my .02