98 Cherokee sport 4.0l 103K miles - so this weekend i installed a new magnaflow cat 94136 and a new flowmaster 40 series muffler 8042541 and new dynomax tailpipe 44171
and 2 new O2 sensors
all stainless but the tailpipe...
anyway, now when i first start my jeep, it will idle fine and then about 30sec to a minute into running it will spit and sputter for about 5-10sec and then run fine... i don't understand it.

only reason for the new exhaust is due to a CK Engine light from the rear O2 sensor being bad and when i went to replace it the rust made it very very easy to remove... so i did the new cat etc....

any help would be much appreciated.

thanks

 

its very possible that you damaged one or both of the 02 sensors when you installed them or they were defective from the factory. The o2 sensors will cause it to run like that. Do you have a check engine light on??

 

no, no check engine lights on now

 

so after some research, I found that the new O2 that I installed in the down pipe was bad from the factory. The heater was not functioning. I purchased a new O2 from RockAuto.com on Thursday at 4:02PM EST and it shipped from CA got it today (NTK) installed and wham!!! like new again.

So I filled my tank and hit my trip lets see if my MPG goes up. I have an app on my phone that I have been keeping track of ever since i got my jeep and my average MPG for the last 3 months has been 13.39

 

What did your 02's look like for upstream and downstream... Which one had more holes?

 

Ummmm. If I remember correctly the down stream had more holes