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#1 03-18-2016 15:30:56

Registered: 03-18-2016
Posts: 1

Non-California O2 Sensor causing bucking.

I have searched many times, but not found anything on this so far, so I thought I would post my findings. 

I have a 1999 2 Door XJ 4.0 STD 4x4 with 215k miles.  I bought it from a guy in California and when purchased it, had a CEL for the O2 sensor.  Got a good deal because it had a CEL and I have changed sensors before it is probably the easiest and cheapest thing to fix. 

Replaced both the sensors with part numbers I got from multiple sources online and assumed all was good.  CEL went away.  However once running the new sensors the system seemed to start bucking.  When cold, I would get a drop of power and then a sudden rush of power, then it would run perfect until the engine was shut off and cooled down again, and the cycle would repeat.   

After a week of this, the CEL returned.  And the "bucking" went away.  Turns out the CEL would put the fuel system into open loop and that stopped the bucking. 

I went into the auto parts store, auto zone, because they will read the codes for free.  When looking up parts they asked if I needed the sensor with Ca emissions or just the OEM replacement.  What I initially installed was the OEM replacement, this time I purchased the Ca unit.  This unit looked identical except the pigtail cable was shorter and the heat protection was orange instead of black. 

Even with the shorter pigtail, the new Ca part still fit.  I installed the new part, started truck, NO CEL and drove away.  The funny thing was I didn't think it had a rough idle or a lack of power, but immediately felt a smoother idle and there was a noticeable increase of power.  I have put 2000 miles on with no issues or CELs returning. 

I hope this give someone else another option if they are having O2 CEL issues. 



03-18-2016 15:30:56


Re: Non-California O2 Sensor causing bucking.

#2 12-30-2017 13:14:28

Registered: 12-10-2017
Posts: 7

Re: Non-California O2 Sensor causing bucking.

Will differential from a grand Cherokee bolt in to a Cherokee xj


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