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I suspect that you have a broken timing chain tensioner. It is most likely the one on the short chain between the two camshafts but it could be one on the long chain also.
That is what will usually cause you to have one side showing rich and one side showing lean. It will usually show up in the fuel trim readings also,they will start to oppose each other. If you have just cleared codes this may be why they read zero? You can verify this with a manual compression test. Just test one cylinder on each bank if one of the cams has slipped due to a broken tensioner one side will read like 190 to 200 PSI or so and the other side will be like 140 or 150PSI.
I run compression test one cylinder on each side, they both show 170PSI
After go to close loop, short term trim read around 22 on both side, long trim around -1 to 4, oxygen read on bank 1 both sensor almost below 450 mA, but on bank 2 front one 900mA, rear after Cat read 1000mA or over
Those compression readings should eliminate the timing.
Thats strange that you are getting a rich code. You should be getting 2 leans codes with those short fuel trim readings.
The one reading of over 1000ma is a little high but rear O2 would not set the codes you have.
I would check the MAF and make sure you don't have a bug or something stuck on the filament and maybe clean it with some electric or MAF cleaner.
that sounds just like a tensioner problem but they will have a difference in compression from side to side.. Have you driven it to see if codes will reset and see what fuel trims are reading then?
You said you have a little noise in the front of the motor does it sound like it is close to the cams?
What I have seen mostly on these when it does this is the secondary chain between the intake and exhaust camshafts usually on the driver's side head most of the time. The plastic piece on top of the tensioner for the secondary chain will break off. This lets the exhaust cam slip a little maybe a tooth. This will cause it to set the one rich and one lean code. And usually if you drive it or maybe run the RPMS up to about 1500 to 2K and hold it for about a minute or 2 the fuel trims will start opposing each other.
I have also seen one that the plastic piece on one of the cassettes broke off but it made more noise.
Will get back with you on monday, Thanks