I need some help with my long term fuel trims recorded by autotap. First off do these numbers indicate a rich, or lean condition, and by how much, is this a percentage?

In cell 11 the drivers side is higher than the passenger side ~2 more throughout. 12.5 vs 10.9

In cell 7 the drivers side is lower than the passengers, ~7 throughout. 6.3 vs 13.3

In cell 16 the drivers side is lower than the drivers side, there is a difference of 8.
17.2 vs 25

In cell 9 the passenger is ~8 higher, 17.2 vs 25

What does this all mean.

EDIT I took more of a look and Cell 3 is perfect, zero for both sides. This is when the car is declererating.

 

You are reading the long term fuel trims (LTFT's) in percentages. Don't overlook the fact that the LTFT has a "+" or "-" sign.... that is what indicates whether the LTFT is adding fuel (+) or cutting fuel (-). If you LTFT's are positive, that means the engine would be running lean, IF the PCM wasn't adding the extra fuel using the + LTFT's.

The place you may really have a problem is Cell 9... if the LTFT is +25%, that is as high as it can go. It may still be running lean, because the LTFT has max'd out.

Look at the Air/Fuel management section in my "scanner" writeup.... I PM'd you the link. Cells are a function of engine load (MAP) and RPM. The low load/low rpm cell is "1".... the high load/high rpm cell is "15". Idle is "16". Coast down should be "17". Open loop and some WOT cases will use "18". If the PCM was adding fuel (+ LTFT) when you go WTO it will use the Cell 15 LTFT's. If it was cutting fuel (- LTFT) it will use Cell 18.

00 - 15 are "learned" corrections, built up based on feedback from the O2 sensors when the engine happens to be operating in any particular combination of MAP and RPM. Cells 17 and 18 appear to be "calculated" from some of the other cells... but I don't know how. Since I gave up my stock PCM more than 3 years ago, I have not really learned a whole lot more about how it works.....

 

Thanks for the great explaination Fred. I also took a look at your link, good stuff. Whats interesting is that I was thinking that the car was running extremely rich, not extremely lean....

Any causes off the top of your head for this?

 

Don't mean to steal the post, but I am also having difficulty with my car... Injuneer, would you be willing to send me the link to the article you mentioned? Anything I can learn to troubleshoot/diagnose my problem will help at this point.

EDIT: Nevermind, I think I found it... On your site...