I have 3 jag ECUs, 2 N/A and 1 S/C. When I would swap them in and out and the STFTs would be all over the place (+- 25%). It wasn't until I performed an O2 orientation on all 3 ECU's back to back that the STFT's were consistent among each ECU. Prior to performing an "orientaion" on all 3 ECUs I'd have to swap the O2 connector for C and D to get the STFTs to read correctly. I can only assume the cars the ECU's came from had O2 sensors A, B, or C, D connected differently than mine, not unusual over time. Tired of swapping the O2 connectors I performed O2 orientation for all 3 ECUs and now the STFTs the same no matter what ECU I use. The more I think about your problem I wonder if you are fighting yourself? Work to get your STFT numbers as close to 0 as possible (mine are -3.9 at idle) and the LTFTs will eventually come down. Jag ECUs seemingly take their time when it comes to updating the LTFT number.

 

Hello Bob, I think that you are on the right track of my condition with the long term being so far out in either direction on either ECM. The long term on the original ECM has come down two percentage points in the last two days. It is probably is a slow wound to heal given the lean condition that occurred. I am going to try a extended free way trip early next week to see if I can move that percentage downward a bit more. I feel like I am moving a mixture screw
very slowly in the right direction. I've gotten the last six of another 95 XJR6 from RMBaker that I might try on my spare ECM to see if the rich long term numbers will move in the right direction, Assuming that the VIN # is a file number that the IDS O2 reorientation uses.

Larry Louton