GoGoGadgetXJ

91 xj 4.0L IL6
Starts right up when cold runs a little rough (idle drop off a little and then recover) not to bad tho. The when it gets up to around 100 it bogs and eventually dies. I'm almost sure it's running lean (backfires through intake)

Tommorow I'm testing the fuel pressure.

Just wondering if anyone can pin point it or maybe have had a similar problem

Appreciate the feed back in advance

hypedonmonster

Hey man, I'm having the exact same problem. Mine backfires through the intake and has a rough idle but it will run and idle fine until it gets up to running temp (180). I dropped my fuel tank and cleaned the crap out of it, I took my fuel pump out and took all the wires off of it and soldered them to the pump, checked all injectors, checked my fuel pressure regulator, checked the flow of the delivery and return fuel lines, cut my c101 (main wire harness which is a major cause of electrical resistance) and solder and heat shrunk all the wires, checked my fuel pump ballast resistor (should be 12-13 volts on one side and 10 on the other).... I'm sure I'm missing something. But anyways it is probably a bad sensor because when the motor is cold the computer has an open loop which usesno sensors but when it gets warmer it goes into closed loop using all sensors. Your best choice is to find a buddy with a computer tester and a renix/jeep adapter and have them take a look at your jeep when it's acting up. Let me know if any of this info helped you. Btw all of the stuff above didnt help me at all but imma hook up a computer today and I'll let you know how it went.

brianrich07

Im having the same problem. Wher is the fuel pump resistor at? mine is a 96.

hypedonmonster

I'm not too sure were the resistor is on the 96. If its in the same spot as my 88 renix it'll be on the drivers fron fender, abot 4 inches away from the radiator. If it's the same, it's a white resistor with 2 orange wires on it.

GoGoGadgetXJ

hey guys ok so...

Backfiring through the intake tells me its lean right..?
so i just put a new fuel pump and filter in before this started to happen.

then i just grabbed my buddies fuel pressure tester and i have 10 psi at idle!! lmao

so i think ive figured it to be a faulty fuel pump ( all hoses are connected right and everthing is working right) except the FUEL PUMP!!

grr all this work for something so simple and a fuel tank drop.. he he he..

and i dont know where it is on a 96 i know its on drivers side around the intake on my 91

cool coll tho ill let you guys know how it went when i replace the pump

GoGoGadgetXJ

hypedonmonster

i didnt really read your whole post (kinda hurt my eyes)

but if your fuel system is working right.

and you say it might be 1 of your sensors
( this happened to me before)

i checked all my sensors and eneded up replacing the collant temp sensor and ignition coil ( they were having problems when the truck got heat soaked)

but thats just wat helped me i would make sure first befor you start ripping things out for no reason