96 XJ 4.0 auto and I'm having problems right after start up. I've researched the threads a bit and I can't seem to find anyone with the same problem. Vehicle runs great with just over 100K on it except after start up and I put in drive. It will start to accelerate normally then all of a sudden no matter how much throttle I give it, it kind of bogs down like its going to die until I hear and feel a kind of hollow "pop" under the drivers side where my feet are and then it accelerates fine and I don't have the problem again until I turn it off and restart it. Also taking my foot off the throttle and then giving it gas again when this happens makes it go away as well. It's not a huge problem more of nuisance but I want to make sure it wont lead to something serious down the road. I can't think of anything it could be and the vehicle has had this problem since I bought it. Any ideas?

 

Sounds like a torque converter issue to me.

 

I would start cheep CO2 sencer.

 

I have the same problem! It is really annoying.

 

Check the O2 sensor near the cat. If itis frayed or cut it could cause a fuse to pop in the power relay center under the hood.

 

I'm changing the o2 sensor tomorrow because i'm getting horrible gas mileage like 10-11 city so we shall see if it fixes it the one nearest to the headers tho not the one after the cat. Ill let you know what I find out. Thanks guys.

 

Could be a clogged cat.

 

Didn't even think about that. Now that you brought that up I'm betting that's the issue. I had the same problem with my rig years ago and it gave the same symptoms.

 

I had a '99 that did the same thing. Would start fine, but just as I was pulling out it would bog some times, pop then run fine. Never did figure it out.

 

So time for a newish cat eh? Theres a really nice all Jeep pull your parts near my house ill pick one up and let you guys know if it fixes the issue. Thanks for all the input!

 

disconect the exhaust and test drive see if issue remains is what i would do

 

My 97 did the same thing, my initial thought was the cat, I installed a test pipe to verify and that turned out to be a wrong idea. I threw sensors at it, tune at it, etc, nothing solved the issue. What finally fixed it, was my down stream HO2 sensor wiring was shot back towards the t-case, I replaced the wires problem solved. Any codes stored?

 

Check out WWW.performance-curve.com

You can get a good exhaust system real cheap there. I'm running their 2.5" mandrel bent system.

 

Update: Alright guys the other day I put in a new upstream o2 sensor and the problem is GONE. Idles better and has more pickup too. Pretty sure I get better gas mileage as well not sure yet have to go thru the whole tank but I was averaging 200-220 per tank.

 

Thanks! It fixed my problem too!! I'm soo happy. Cuse it was rather embarrasing when a cute girl is walking and your jeep backfires.