hello folks,

I get an intermittent check engine light on my 97 XJR, and codes are for both O2 sensors on bank 1.

After I reset them, they stay off for a few days and sometimes after a long highway drive, both codes come back and check engine comes on, and sometimes I don't get any codes for a week.

I have a hard time understanding why both sensors on bank 1 would call it quits at the same time, so it must be another anomaly, perhaps a rich fuel mixture ... but if that's the case, how come it doesn't trigger anything on bank 2 sensors?

Since bank 2 sensors don't give any fault codes, I'm beginning to rule out incorrect fuel pressure or a faulty MAF. I am neither seeing any evidence of an exhaust leak on bank 1 (no black sooth), nor do I hear an exhaust leak.

what else is there to check? a leaky injector on cyl 1, 2 or 3? if so how would I check that?

any additional thoughts on what may be triggering both sensors on bank 1?

thanks in advance