o2 sensor?

Ok so i have posted this in soo many forums, i thought that this should be good one to try. I have a 96 4.0 straight six with auto. When i got it when at a idle it would shake. It was noticeable on the steering wheel and in your ass. lol Though the tack does not jump, i have changed the iac,tps, plugs,wires,cap,rotor,fuel filter, clean throttle body, seamfoamed tank and throttle body, though no difference. There are no codes, drives fine after hit the gas, passed smog. So i put the scanner to it, it told me that the upper o2 was going crazy it was going from rich to lean to center back and forth. I was wondering if the o2 would make it shake

How are your motor mounts? The 4.0L eats motor mounts. Is it possible that the drivers side one is shot and the motor is moving causing the vibration?

They look fine.

I just do not know what to do now!! IM GETTING SO FLUSTERED!! I have spent so much money in this motor to get it running good and it seems that im never able to solve the problem? I wish that some one had the all knowing aswer. lol I just want to be able to make sure that my vehicale is good in the motor department before spending money on the suspension etc!! I have looked at the motor mounts though there is no sign of cracks i notice that the driver side one the rubber on the firewall side you are able to stick your finger between the rubber and the mount? Is this normal or could that be the cause. Though when the jeep is running, you put your hand on the exhaust you can feel it hick up and sputter every so often? SO IM JUST SOO LOSSED!! IM AT THE POINT OF GIVING UP.!!!1:huh:

what about timing ???
also possible clogged injector cuasing a miss, run some MMO through it for a few tanks of fuel it will clean things up and improve MPG....

or have a buddy get in your jeep with E-brake on and put it in D than go to R and watch the motor for excessive movment from side to side, if so than the motor mount is shot.

My 02 sensor was bad in my 93 and cuasing a sputter or loss of power at start out in 1st and 2nd gear, it kinda acted like I was letting out the clutch without any gas... It passed emsisions (or so I was told by the seller) and did not show a CEL, I replaced the sensor and all is well.
I would not question replacing it weather it fixes your problem or not it is normal 100k mi maintanence.

also if your using "house brand" sensors (other than napa) than its posible you got a bad sensor out of the box, I'm new to XJ's but have driven jeeps (ZJ's and WJ's) for years and I don't waste my time with non mopar sensors in either, they are salty but they work !

Unplug 02 sensor then start it up.

You will have a check engine light but you will also have your answer.

Might be a combo of 02 and engine mounts.

I unplugged upstream o2 started it for about thirty seconds. No code no difference. Do I need to wait longer?

you are able to stick your finger between the rubber and the mount? Is this normal or could that be the cause.


pretty sure you need new mounts

I know its not a motor mount because if you put your hand on the exhaust while its running you can feel every couple of second it puts, then tries to clear it self. Also you can see it in the motor compartment.