Hi guys newb here I got a 99 4dr 4.0 it keeps having issues stalling after start up cold or hot and sometimes idles low 1 bar above 0. Also on acceleration the cel will flash. New dist cap, wires, champion copper plugs, crank sensor, stator/cam sensor, cleaned all grounds and connectiobs newer battery also replaced IAC,tps and map. I put in injectors from Ford focus' the blue ones others have used them runs fine idles fine after few seconds that was a battle at first. It had 3 vacuum leaks 4 different spark plugs out of 6 and two wires to rear o2 sensor sheared it did run rough. 129k miles runs fine down the road I don't feel a miss it did have p0300,303,304 as well as rear o2 sensor circuit high code and evap code rear sensor may need replaced even after fixing wires but unplugging either makes no diff, the evap large leak code is from the metal line from gas tank to black box it's rusted the one with rubber connections. The Xj has been in my family for 15 years I got it given to me because my mother thought it wasn't worth selling it ran terrible I've made it almost perfect night and day difference like it used to be when I drove it years ago. Air filter is also new injectors were like new from a wrecked car that was mint and a low mileage car no dirt on either and run injector cleaner. I seafoamed engine as well as ran half a gallon slowly through intake to steam clean the carbon out it don't know tick use oil or coolant has plenty power. What am I missing the crank sensor junk? Last one went out and had no spark but ran no different after swapping in one from a jy I do have a new one as a spare and probably 3 of every other sensor and 3 spare sets of injectors tried swapping wires cap and rotor no change i can't hear or feel a miss like it did have idles fine I'm proud to say because it didn't at first help me figure this out took valve cover off all is fine oil is always clean no funky exhaust smell or fumes. I put a Flowmaster on dumped with a turn down tip although it sounds like a Sherman tank I know it's not this. I've worked on many vehicles I'm good at diagnosing this one has me stumped signs point to Cps no the fuel rail doesn't loose pressure, IAC may need swapped again I noticed idle will drop sometimes when stopping but only died once main issue is start up. The flashing Cel it's did it even before swapping out sensors and tried others since I'm stumped I'm chasing my tail. Sorry for the book guys all help appreciated I only have basic tools I used to have a very impressive collection of truck brand tools but entire garage was cleaned out stolen and was a killer. So further diagnosing is hard aside from swapping parts funds are tight I am the only one working and so far it has been cleaning my pockets out it's my only vehicle and I live in the boonies.

 

Future punctuation would be appreciated. Is the CEL flashing when it stalls? Flashing CEL means active misfire and the engine could be stalling to prevent more damage. The problem with replacing so many parts at once is one may fix the problem but another could be bad out of the box and recreate the problem. What brand sensors did you get? Auto part store sensors are notorious for being bad out of the box. Here is a good thread about what brands we've had good luck with.

 

I tried generic sensors but then went to the junkyard and bought multiple factory ones.
The vehicle has had the same codes from before replacing anything.
I just went to advance and used the Actron scanner ,used the live data and checked 02 voltage which was 1.0 on both with key on engine off. Map reading was normal engine on tps was fine.

They all were baffled after explaining all I've done. I didn't just do it at once this was little by little followed by resetting ECU. Which I followed instructions even used scanner they pop right back up.

​​​No sensor is suspect other than Cps but it's replaced with a low mileage factory unit also same codes from before any repairs or part swap. The CEL only flashes after heavy throttle or load when I let off the throttle with no noticible shudder nothing or sound.

Could it be weak fuel pump? It drives fine and if it stalls it's at start up and rare and random. Any ideasv3colllññ

 

CPS wiring is suspect.

It is NOT a weak fuel pump.

Also check the wiring to the coil. Sometimes that connector gets flaky.

 

I changed the coil wire connector because the new coil used a different plug same color 2 wires though, old coil had cracks also is it normal to feel the coil pulsing while running even in the wires.
The cps connector contacts were clean and if you jiggle it while running has no effect and I traced the wires on both ends found no damage.
My gut points to Cps it is a junkyard sensor and really it came off a transmission already pulled with no markings ,wire was a hair shorter but fit fine and looks the same but I have a brand new one to try... I'll give it a go they sure are a pain to change.

These dang 4.0 engines sure are picky like a Swiss clock everything has to be just right.

 

Get an extension set from Harbor Freight, and tackle it from underneath and behind. Add a universal joint on the end, but wrap some duct tape around it so it doesn't just flop around. Once you are solidly on the bolt, the tape will flex enough.

 

Edit:

Scrolled too far and answered the wrong post