UsmclovesXJ

93 Jeep xj
Automatic aw-4 trans.
Ok so my jeep was ran with out an o2 for 2 years. Not my fualt.
Put in new o2 and took her out for a spin. After every shift comes a loud *** back fire?
I drove for a lil bit come back home and disconnected the o2 and went back out. Bam. She's fine no back fire.???? Wtf?
I buy another o2 thinking my NTK was screwed this time i bought a Bosch. Same thing put it in now back fires after every shift of the trans?. In short no o2 = no backfire
With o2 in= backfire.
Any idea what's causing this?
Also no cel's while thats happening.

Knucklebuster

LOL, I think you,ve been outsmarted by your ECM computer. disconnect the battery for 20 minutes with the headlights and ignition on. Re-connect the battery and take it for a ride, a little highway and a little in town. Without that sensor, it told the motor to run way rich or lean, and now it has to re-learn the fuel to air ratio.

UsmclovesXJ

All I did was disco the battery for the whole install. 5 Min?... But I will give that a shot

eriejeep

any luck on that repair? I'm having the same problem - rear O2 was shot when i got the jeep, i put 2 new O2's in and now when i start it, it will idle fine for about 30 seconds then put put put backfire then run fine....

UsmclovesXJ

yeah buddy had to reset my ecm and found out I had a vacuume leak. Fixed all that ran some seafoam and bam. She's good.

Lostfisher1

i bet ur gas millage went up a bit.

VTJeep

For a year and a half mine did this, no CEL, finally diagnostic machine says bank 2 o2 sensor was all over place. So after pretty much everything new under hood, except the alternator, injectors and ECM, and then the new o2 sensors it was still acting up. So finally dropped gas tank and discovered a bunch dirt and leaves kickin around. Got it all clean and running well, but still with CEL on.

Long story short- I go to shop this am, check and clear CEL, at exactly 50 miles, right after getting gas, the CEL kicks on and it's starts to buck, chug, and pop (backfire) at the manifold.

Not to high jack, but it seems similar, and I've been thru the ropes with it... I'll post all about it if I ever figure it out...

UsmclovesXJ

So much better gas mileage.


And leaves in the gas tank ??...
mAybe an ignition issue ?
Ever get your cylinders pressure tested?