new here to the forums, been looking over them for the last few days, but i have come into some really aggravating trouble, and looking for some guidance. hoping maybe someone else has ran into this before.
Vehicle: 91 YJ 2.5l EFI, 5 spd
started out missing & stumbling real bad @ 2500 rpm, so i replaced the fuel filter, filled up with 93 octane, & added a can of sea foam. runs fine at start up, but when it gets to operating temp (170-190) will start idling @ higher rpm's, sometimes stall out, on its own, or die by pressing throttle pedal, sometimes backfiring when it does die. let it cool down, runs fine again, until it gets up to temp.
this morning, i took a video of it when it got to operating temp.
after you shut it off, or it dies, whichever comes first, it will not start until it cools back down.
after the video, i replaced the MAP sensor, replaced the Coolant Temp Sensor. replaced the coil, coil wire. havent done the intake air temp sensor yet, they put a coolant temp sensor in the box, so i have to run back to the parts store to exchange. got up to operating temp., ran it for 8-10 mins, everything seemed fine. but it still does it. if you do get it to run, it will idle fine, but if you touch the pedal, it just dies, like turning the key off.
codes ( given with the key on-off-on-off-on method):
12- battery (self explanatory)
33-a/c circuit (no a/c)
55- end of diagnostics
i looked at the cat. converter, its a very dark gray on the bottom side, wondering if maybe it plugs up when hot? idk, never had one do this.
Have you replaced or checked the Throttle position sensor?
no i haven't, i assumed (and you know what they say) that because it ran good until it got to temp., it wasnt it. but i will give it a shot too. i have to go return the coolant temp sensor thy gave me in place of the air intake sensor.
Had an xj with the 2.5 and it did this same sorta thing, turns out it needed a new fuel pump, might wanna check that too.
already checked, but forgot to mention it. fuel pressure is 37-39 lbs. and fuel pressure regulator is good as well, pressure increases 9 lbs. when its unplugged.
this was actually my first thought, and the first thing i checked. i had a suburban that ran great at idle, or out of gear, but spit, sputtered n popped under load, & after i replaced every electrical part on it, i figured out it was a bad fuel pump, not giving enough pressure.
will run a little longer, idles flawlessly at operating temp. but will just shut off at random. cranks right back up, idles smooth, has hesitation when you give it some throttle, & stumbles @ 2500, let off the throttle & sometimes it returns to idle, sometimes it cant recover & die, but will restart (didnt restart before when it was up to temp.)
i did find that the o2 sensor has an issue. the harness coming down to it has chafed wires at the pigtail & arcd out on me against the frame when i moved it. i cut the wires back behind the bad spots & taped them (leaving o2 sensor unhooked, & restarted engine. stills idles good at temp., still hesitates when you give some throttle, still stumbles around 2500 rpm, but no check engine light is on with the o2 sensor unplugged.
after calling several auto parts stores to discover that while they do have a part number for the pigtail to go to o2 sensor, they do not stock it. dealer only item. call local dealer down in Orlando this morning, only to have them tell me "We do not sell the item, due to fire hazards, BUT, for $790.00, we will sell you the entire wiring harness, which will have the plug you need."
after regaining my composure, i drove 6 miles to one of the local junkyards, went on a search, found a "cherry" cherokee with no motor or trans. (very easy access) for a donor vehicle, clipped off the pigtail, payed 2.00 at the counter, and was on my way.
came home, butt connected together, taped heavily, rerouted, installed new o2 sensor, and once again, she runs like a champ!
electrical has always been my demon, dont like it, & get very, very frustrated dealing with it.
so now, on my way to return all the parts that i didnt need in the first place.