Bob_esper

ok my 99 jeep with the 4.0 and at has been acting up recently. when i start it up it will run fine for about a minute, then it will start missing like crazy for about 1 minute then it just fixes up and runs fine for the rest of the time. usually when it does this it will start to stall then it will pick up before it dies, well tonight it died, but it started right back up just fine

Bob_esper

last fall it did something similiar and i replaced an o2 sensor and it cleared up... oh and if i shut it off while its doing this when i start it back up its fine

Bob_esper

anybody?

Big Bess

Hey, I am too looking through the threads for some info on my 89, I recently purchased out Jeep cherokee and it too had a miss an would die for no reason. It would begin to Idle rough, but would start right up. We began to suspect injectors and ran the B-12 treatment on a full tank of gas and then found that there were leaks on the injectors that I had over looked cause they were small and when running the idle up manually I could see the leaks were coming through the plugs and o-rings too were leaking. We replaced three injectors and all the o-rings on all injectors. it seems to be running fine now. just something to check into.

fantic238

First thing, you have to find out wether it is an electrical problem or a fuel problem. Sounds like something related to temperature increase.
Any codes?

Bob_esper

the light has never came on.. what makes me think its a sensor is that it just magically goes away lol it is like someone hit a switch

Bob_esper

ttt

Bob_esper

anybody? was hoping to get this thing fixed this weekend

davida

I had this happen a couple of times in my 96, never could figure out what it was, I always blamed the fuel injectors or water in the gas, I thought it was something fuel related. It happens exactly as you say

Bob_esper

hmm yeah mine started out doing it every now and again but now its doing it evertime i start it up. its doing the exact same thing it did last fall and i replaced an 02 sensor and it fixed it, could it be another 02 sensor going out?

fantic238

Could be the o2 sensor heating system.

Bob_esper

yeah i heard the heated o2 sensors tended to fail, how many are they on a 99 4.0

fantic238

2

Bob_esper

okay so maybe ill just go ahead and replace the other one... cant hurt can it lol, it has 140k on it and i doubt much of anything has been touched on it before i got itat 118k last spring

TrekkerJmm

@ Bob_ESPER I sent you a PM that may help you out...Tj