Interesting little development on my XJR. Well, maybe not all that
interesting, but anyway, here’s my rambling report…
For ages I’ve had a P0430 code and long term fuel trims seemingly fixed at
about -98 while short term fuel trims hovered just above and below “0”.
Never isolated the cause…and never tried all that hard, either, as the car
Anyhow, during the course of a major servicing and general futzing about I
happened across loose air injection fittings where they screw into each
manifold. I tightened them up, of course, and then (a couple days later)
thought I’d scan the system to see if things had changed. They had.
Code P0430 (B Bank cat efficiency) was gone, replaced by P0420 (A Bank cat
efficiency). And…LTFT had already swung from -98 (both banks) to +50
(both banks). STFTs still seem pretty good, with B-bank running 0 to -8 and
A-bank showing 0 to +6.
But, that’s not all…
Now its two days later and the P0420 has not returned …BUT… the LTFT
is back to -98 and STFTs unchanged. !! Arrrrghhh!
All four oxy sensors vary voltage well enough, seemingly…that is, none
appear dead or even lazy.
I’m not quite sure what to make of this. The LTFT changes occurred faster
than I thought, but there you have it. And, if STFTs have been OK for 2-3
years, why do I show abnormal LTFTs at all?
Any clever thoughts, or even rude peasant curses? The archives reveal quite
a few suffering from LTFT issues but there doesn’t seem to be a magic
Has anyone tried clearing the LTFT cells just for giggles? Could this be a
I’m not wringing my hands with worry here but I wouldn’t mind getting to the
bottom of it. Maybe this weekend I’ll look for any other exhaust or air
Cheers and thanks
Longview Washington USA