on, off, on, off, but mostly on

My check engine light had been on for a while and I found out that there was a crack in the manifold so I welded that up and reset the codes to get the light off. Not even 20 miles later it came back on. I had it tested and it said I needed new O2 sensors so those have been replaced. I was able to drive like 300 miles this time before the light came back on. During this whole time the xj seemed to be hesitating when I pushed on the gas and had a good delayed response. I went and had the codes pulled again and the computer said that it was a bad O2 sensor. How can this be since I just changed both not even a 1000 miles ago? It seems like with the hesitation that it's having it would mean that it's running lean, so would the map sensor be the cause of that or would it be a clogged injector? If so how do I check those? Also why would it be saying that the O2 is sending a high voltage signal?

Nobody has any idea of what I could look at or anything?

What year is you Cherokee? The newer ones have two O2 sensors. One at the cat.

I changed them both at the same time. It's a 98

my boss's suburban was having the same problem, everyone said it was a bad 02 but after we replaced the cap, rotor, plugs and wires it ran just fine, the hesetation was gone. I know it isn't an xj, but it might work.

Update: I figured out that it only seems to hesitate on the first sharp turn that I make after it has been started. It hesitates quite severely which makes me believe that it isn't getting enough fuel or something like that.

90NHXJ said:

What year is you Cherokee? The newer ones have two O2 sensors. One at the cat.

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'00-01s have 4. Two in the manifold befor ethe pre cats and 2 after the precats.