99 TJ Keeps Dying

[Rock Hound!]

I had posted a while back wondering if my fuel pump was going out, well I do not think that is the issue. Here is what is happening, does not matter if the engine is hot or cold. Normally starts occurring at low RPM's 2000 and lower driving through town or when sitting at a standstill at idle. The engine will start to die out, if you try to keep it running it will backfire through the intake and exhaust. I keep pumping the gas quickly to keep the RPMs up but it is like there is no spark nothing is happening and can only peek the RPMs up to about 2000. Impossible to put any load on the engine, if you let it idle will drop down to about 300-400 RPMs and die out. Will not restart, it tries to, and if it does fire up it is running bad... backfiring. If you let is set for about an hour, come back and start it, it runs like a champ no issues. So far I have replaced:

Crank Sensor
MAP Sensor
New Cap and Rotor
Unhooked the upstream O2 Sensor
I have removed the throttle body and cleaned the Air Idle Control Valve

I have read allot of forums on different stories, easy to get confused on what to do next. I was thinking about changing the coil out tonight. Was reading something about the screws on the computer shorting the system and having to back them out. I have not done this yet.

Please help this is getting very frustrating

 

[RockChucker]

how is your battery? my battery was almost dead, the jeep would barely start, and the only way to keep it running was to stay on the gas...

also, is it running super rich? have you had your injectors tested? how about the camshaft position sensor (the sensor in the distributor)? maybe the pcm is bad? do you have a buddy with the same jeep you can swap computers?

sorry i'm not much help, just trying to give you more stuff to spend your money on

but seriously, problems like this are a pain. best of luck to you.

 

[rockreligious]

first thing I would check is vent on gas fill tube, sometimes you can just open gas cap let off vacuum and it will run, sometimes you have to actually disconnect (quick connect) the fuel line off the fuel rail, let the pressure off then re-connect and see if it starts.

 

[Rock Hound!]

Last night i drove around town hoping to get the jeep to do its thing. I parked it at my buddies place and left it running in the drive way. Well after about 15 minutes it started to die out. This time it would not start, again I checked the fuel pressure by pushing in the valve with a scredriver. I have done this in the past and it would allways spray out, thinking it was good. Well the gas did not spray out, just ran out slowly. So i started thinking fuel pump again, checked power going back to the pump and good to go. But the pump would not run all the time when turning the key on. So i replaced it last night and so far running like a dream. I was thinking back and all the times it would die i would have 1/4 tank or a little more of gas. Thinking the fuel pump was getting hot and stop running. I am not one of those guys who keeps the tank full all the time. My neighbor works for an auto store and said in the past couple years with fuel cost they have sold alot of fuel pumps becouse people do not keep there tanks full, and gas is what cools the pump. So hopefully I have finally figured it out:thumbs:Not sure how much a fuel pressure gage cost, but I may have been able to figure this out a while ago if I had one. Just becouse gas sprays out does not mean it is good presure to run.....