i have a 93 engine, transmission and transfer case in the body of my 96 xj. it is in and running but is starting to lose power. it runs fine and makes decent power when it is cold. when running slow and hot however it starts running ruff and missing on at least one cylinder. get it out on the road ans let it clean out and wind up it seems to return to normal but as soon as it is no longer pulling and using the power it falls off again. the problem gets worse and worse as the temp rises. has any one else had a problem like this before? and ideas would be great only lead so far is it is possibly the fuel pressure regulator. possible or not.


again any ideas would be great. just ask if there is anything about my concoction of a vehicle. 4.0l ho .5 speed

 

Cps is acting up

 

but if it was the cps i would not be able to start it again. when it stalls it is like it is due to flooding, and i can restart it right away idles ruff, and and runs like it is missing when given any throttle some times backfiring. by 2000 rpm in 2nd gear the misfiring goes away and it cleans out. but as soon as i slow to a crawl or stop at a traffic light the problems all come back. i will look into the cps to be sure, but in the mean time any other ideas?

 

How your throttle body has it been cleaned and wen was your last tune up

 

very due to be cleaned. bought it as a junk yard dog. little has been done to it. and im sure there was less maintenance before i put my name on it . i know all of this will contribute to my problems but im trying to find the main cause of the problem before i clean it up just an effort to learn something more then just that i should keep it maintained.latest i have been given is that it might be a coil well on its way out. this sound like something possible?

 

Sounds like you have a case of heat soak. You have CEL on? Any codes?

 

no check engine so far. this after noon i tested the fuel pressure it checked out even under spec which caught me off guard. but was not constant jumped between 30psi and 40 psi this was in its worst of conditions the engine struggling to not stall as if out of fuel or fowling plugs. got advised on putting a new coil in it. i pluged one in and went for a spin. first test it worked. got it up to temp and and it never missed so problem fixed???? so far so good i guess not i have to get the coil in and solid. then more testing can continue and another fuel pressure test when it is running smooth. still lacking power. tho. could be just me wanting to much from the tired old 4l but .... defiantly missing something. will feel good going ahead with a tune up new cap/rotar/wires plugs along with some new fluids should help my poor rig feel better. what is it you mean by heat soak? this is a term i have not heard before.

 

Sounds like you're going good with the coil! Heat soak usually refers to fuel starting to vaporize before it is dispensed by the injectors. Since the intake and exhaust manifolds are stacked, pretty much all of the waste heat infiltrates the intake system. In late-model XJs it's bad enough that Chrysler released a TSB that instructed wrapping the #3 injector in heat-reflective something. Lack of airflow in the engine bay and warm ambient temps can contribute to heat soak. Running lean or a restrictive exhaust could also do it I suppose. A nice way to deal with heat thrown off the exhaust manifold is to stuff some aluminum plate between it and the intake.

 

new coil is in solid now. seems to have fixed the main problem. order a tune up kit so maybe next weekend or so the parts will come in , and it will get new plugs wires cap and rotor. i will have to look into the heat soak issue maybe wrap my intake, i am not sure if mine will suffer from it where i am living right now i'm not sure the temps are hot enough,but it could not hurt. thanks for the advice.