I would like to get some input on the importance of long term fuel trim readings. I drive a 2002 2.5l automatic with a little over 118,000 miles. I currently don't have any active dtc codes but the P1111. My concern is that the ltft readings have quite a bit of disparity: 6.3 (Bank 1) vs. 3.1 (Bank 2).

Brief history on car: Around 3 months ago, misfires on all 3 cylinders in bank 2. My mechanic confirmed a slight coolant leak into combustion chamber. He re-torqued the bank 2 cylinder head--no loss of coolant and misfires since. P0430 code (catalyst inefficiency) kept coming back, so I installed a spacer between the downstream oxygen sensor and the catalytic converter. Code hasn't returned after this quick fix. In fact, car just passed a strict california biennial smog inspection.

Any response greatly appreciated.

 

No one appears to want to stick their head above the parapet on this one.

The misfires may have compromised the Cat or you could have a borderline downstream O2 sensor on that bank.

If the vehicle was mine and it had just passed inspection, I'd be leaving it well alone with an occasional check on DTC's!

Graham

 

'Took your advise and just left it alone while periodically monitoring the readings. Around 3 weeks ago, I decided to replace the fuel filter as a maintenance measure when the car turned 120k miles. Old fuel filter contained a considerable amount of impurities (black/brown stuff). My latest readings now indicate 0.8 (bank 1) and -0.8 (bank 2). Not sure if the fuel filter replacement or the car's computer learning my conservative driving style had any effect in the improved ltft's. But, I'm starting to notice improved mpg.

Thanks again for the advise.

 

Well you really shouldn't expect the two sides to react the same if one side has a modification to it.