whats up guys new here but not new to cherokees. had mine for almost two years now and i love it. now the bad it has a slight miss fire very noticable at idle. new stuff ive changed include knock sensor, o2, coolant temp,map, brake booster and master cylinder , cat converter. would a bad injector or the throttle position sensor do this. its an 88 with the 4.0 and aw4 also new coil wires cap rotor and spark plugs
thanks guys for the help

 

you may have a partialy clogged fuel injector.

 

Every once in a while i have to push down and pull up on my #2 cyl fuel injector. its weird if i push down on the injector plug it mis fires if i pull up slightly it works again. give it a try on each injector while it is running see if you have the same problem as i do.

 

cool thanks guys ill have to try that

 

also i have run lucas through it with no change should i take them off and soak them in carb cleaner.

 

 

yes vary noticeable at idle and i did mess with the injectors with no luck

 

check compression to c if it is head gasket

 

but if the head gasket went wouldnt i have water in my oil and i dont also i changed the fuel pump a while back if that helps any and when i get on it i dont notice it at all

 

then what i would do is find out wich cyl is causing your problem first. when the enging is running un plug 1 injector if the engine runs rougher that cyl is working. plug it back in and move on to the next. till you remove one where there is no change. that is your cyl with the misfire. then we can work from there.

 

i did try that and did notice number four didnt make as much of a difference as the other ones so maybe its only partially clogged

 

It needs to be changed every year

 

Then i would swap the plug with another cyl. re-check the frieing order make sure 2 wires are not mixed up. i did not see in your first post ' did you change your fuel filter? it is located under the xj on the drivers side on the frame rail near the back. a part clogged fuel filtermay limit your pressure at the fuel rail. its a long shot but i still would replace it any way. also if the injector is shooting fuel but still miss firing you would notice a bad raw gas smell on the spark plug as soon as you shut down the engine and pull it out asap.

 

ok i did change the fuel filter 5 months ago so that cant be it so i was actually thinking about geting reman ones from presisioninjectors down the road so maybe i can live with it for a while in runs good down the road but its bad at idle but my idle is good when its cold and when it get to operating temp it misses like what im describing

 

did you check for vacuume leaks?. that will do it too. if you can get your hands on a comperssion tester i would def do so to rule out bad valve, head gasket, rings ect