im about ready to put a bullet through my engine block so i will have to do a complete motor swap.... ive read dozens of threads just cant figure it out


I have a 98 cherokee..... 4.0 auto matic......
When it is running it has a noticable misfire.... All of a sudden it started once i drive and leave it idling in park it sputtered and almost died out today....

Ive replaced the plugs with bosch platnum plages all gapped correctly ive double checked....
Wires are new
Rotor is in good shape...
Took the dist cap off completely lightsanded the points and cleaned it....
Still nothing helps it (ive also reset my computer)
My check engine light is on throwing codes
1) misfire
2) o2 sensor ( i only have 1 o2 sensor which is upstream the other one is removed) i think thats why im getting that code (correct me if im wrong)
3) ignition starter switch ( ive bypassed that with a regular switch)



PLEASE HELP BEFORE I GO INSANE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

pleasee????

 

I am making a big edit to this post of mine.. Deleting the original and retyping it.. (I totally didn't pay attention to myself when i read it originally)
The o2 sensor that's missing is causing the code, yes. And it's probably causing the misfire as well.

 

Other parts

TPS
IAC valve
Fuel delivery components- pump/filter assembly, lines, injectors.
PCM, but I think you said it was ok?

Have you pressure tested the fuel at the rail?

 

alrighty then......basics......DOUBLE DOUBLE check firing order...(i.e. wires from plugs going to proper location on distributor.

Bosch platinum are NOT so good for the 4.0 L engine. use the copper

gapped at .035. (autolite, or champion)

replace O2 sensors....(it matters)

put pressure gauge on your fuel rail an see what you are reading for fuel pressure. (might be your regulator is going.)

when is last time you changed fuel filter?

get new plug wires.......physically inspect them to ensure no cracks or lacerations in the wiring on each one. also ensure you hear/feel an audible "click" when you put the wires onto the spark plugs.

new cap and rotor is recommended.

also only put plugs in to tightness that feels good-n-snug....tight,but not godzilla like.

good luck sir let us know whats what!

cpnwrench

 

HEEEEEYYYYYYYY!!!!! VTJEEP beat me too it....!!!1


see, I told everyone I type S L O W



cpnwrench

 

My Jeep is having the same problem, recently it started just dying on me. My mechanic put brand new bosch platinums in which at first stopped the misfire, then a day later it started back misfiring on the same cylinder (2001 4.0 automatic). I heard it may have been the coil pack, so I replaced that as well today. Fired it up, it ran for 5 minutes then was still misfiring and then stalled again. I need help. Now I am hearing it may be fuel filter, could that be?

 

I thought maybe sense the 2nd o2 sensor is missing then it would mess it up but ive personally talked to 3 people with jeeps they dont have one so dont see why mine would be special? lol

How do i check the pressure at the fuel rails????

 

Also does anyone have a link or instructions on finding/changing the fuel filter???
im used to chevys sorry this is my first jeep

 

with a fuel pressure gauge

autozone will rent you one i thinks

cpnwrench

 

buy the haynes manual for your year (lots of good stuff)

for starters,, then as you progress into wrenchdom and jeep religion you can get the ............bible......


yes sir the word, the gospel, the "shop manual" ahhhhhhhhhh!


cpnwrench

 

Also, While i have a GUT feeling it has something to do with fuel........


Would you guys replace the Fuel module or fuelregulator first???
MIGHT i ADD that my gas gauge doesnt give a correct reading also

 

sir, do the basics first.


cpnwrench

 

don know about the 98,,,, my fuel filter is under the jeep drivers side near rear wheel.....

cant miss it.

cpnwrench

 

Mine is not ive already looked at that spot....
From what i read.... the only other spot is above the tankk