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View Full Version : 4.0 will not start or run by itself

Mike H.
03-13-2006, 10:10 AM
if I add throttle when turning over, it'll start, then shut off.
once started, I can make it run by modulating the throttle, but, if I let off it's shuts off.
rig is a daily driver, and has worked flawless (even yesterday) until this morning.
all guages read fine, and no check engine light.
all electical connections around throttle body and injectors are plug'd in.

Any ideas?
twstdtj
03-13-2006, 10:17 AM
Sounds like the computer took a dump. Ive had it happen to me a few times. Go drive it it should clear up. Mine has always happened if the battery was disconected for a while though
desertdawg
03-13-2006, 10:27 AM
My son's XJ did the same thing and it turned out to be a bad TPS sensor.
desertdawg
03-13-2006, 11:48 AM
It could also be a bad fuel pump or fuel injector.
Special K
03-13-2006, 11:52 AM
I hate to add another cause to the mix, but my TJ had the exact same problem and it turned out the fuel injectors were clogged.
Tom M.
03-13-2006, 12:23 PM
I agree since it sounds like the engine is starved for fuel. You might to check or replace the fuel filter first. If it has been awhile that filter could definitely be clogged. Then check the fuel pump, injectors etc.
wannabejeeper
03-13-2006, 12:46 PM
What year did the filter go internal? I could be wrong, but I thought they've been internal for a while now. I would venture that it might be the pump, if you can, check your fuel pressure first.
jeepin_in_az
03-13-2006, 12:50 PM
How about the battery? Sounds strange, but if the battery is dead, then it will not idle. Check the battery, even if you *think* it is fine.
Antman
03-13-2006, 03:49 PM
How about the battery? Sounds strange, but if the battery is dead, then it will not idle. Check the battery, even if you *think* it is fine.

X2 I agree with this one. Had it happen. Engine would start but then only run at higher rpm.

Good Luck! Lets us know what you find for a solution.
Mike H.
03-13-2006, 04:35 PM
is there a scherader valve on the fuel rail?
is a guage easy to find/use?

I have the glourious in tank filter.... ahhhh.

I have a good battery in my '69 F250 that I'll try.
I used the XJ to charge my cell phone on the w/e... but, wife has been to Target and back since then...
jeep4offrd
03-13-2006, 04:40 PM
I just had this very thing happen to mine. Turned out to be the fuel pressure regulator. Replaced it and a new fuel filter, and so far so good. Just passed emissions this morning.
wannabejeeper
03-13-2006, 05:30 PM
there should be a valve on your fuel rail, all you do is screw the gauge on and start the Jeep, I'm not sure what the pressures are supposed to be, but I can ask my driveabilty tech in the am.
Mike H.
03-14-2006, 07:13 AM
seems the first post was dead on... computer.
i disconnected the battery last night, hooked it up this morning, and whamo, rig fired right up and idled fine... the old computer reset... who'd have thought it'd be that simple?
Wife left for work at 6:30, and I've not recieved a call... so all must be good.