Just fitted new low pressure fuel pump, fuel filter and PCV. Fuel trims looked fine at idle and load at 0% as normal. Went for a drive to warm it up and noted whilst stopped, Bank 1 LTFT started climbing negative to minus 20-30 then started going positive 20-30 then back to zero then again back and forth positive and negative. Continued driving trims continued to stay at 0%. But at idle, Bank 1 continued to either go negative, positive by large amounts or remain at 0%, randomly. Not seen anything like this so not certain what to make of it.

 

air in the system??

 

Following up on this, not really any conclusion. Performed a fuel adaptation reset but that did nothing, replaced PCV but the one removed was fine (about 2 years old?).

Now valve covers and breather tubes replaced (valve cover gaskets long done, breathers fine but all new regardless considering the number of times they've been R&R'd, wanted tighter fitment) along with loads other parts. First drive the odd LTFT behaviour switched to bank 2 but engine performance perfectly fine and by the time the first 50 miles done after this service, LTFTs on both side stabilised to 0%.