I was wondering the same thing when I saw that posted over there. Glad to hear the answer about it from Bill also :thumbs up yellow:

The rest of the story!
 

Like Paul Harvey used to say "and now the rest of the story".

Turns out sml175's problem began at the stock program level added a tuner to make it better???

The stock program was the culprit not the hand held. Kinda felt like Jack and Bill for awhile not getting all the info up front is kinda frustrating.

Lars

It IS frustrating when you're blundering around in the dark, isn't it?

But, all this discussion has brought up a question that has been in the back of my mind for a while. I guess this is to the Mad Doctor too.

If a lean problem is seen in "open loop", i.e., WOT (in most cases), would increasing the WOT fuel have any beneficial effect? I guess what I'm asking here is does an increase in WOT fuel uniformly lower the A/F ratio across the open loop table? Or, does it just somehow make more fuel (if needed) potentially available, maybe at or near max rpm?

Open loop doesn't always have to occur at WOT. There are functions that control open loop based on a number of different factors, most particularly load.

The WOT multiplier controls how far the fuel adjustment can go in order to achieve desired AFR for peak torque. This is more of a limiter in the sense that it won't allow any fuel adjustment beyond a certain point. Outside of that, the main fuel tables are what offer final adjustment of open loop fuel while the MAF sensor provides the air mass values to the PCM so the PCM can have a base to maintain the target AFR of 14.64:1 in closed loop. Short and long term fuel trims take care of everything else.

I knew Open Loop didn't mean just WOT, but I guess I WAS confusing the two when I talked about WOT fuel, wasn't I? Sorry bout that!

Isn't there a limit of some sort on the possible adjustment available in the Closed Loop fuel trims? In other words, if things are badly out of adjustment, it may not be possible to achieve the desired A/F ratio? I seem to remember reading this somewhere.

- Jack

There is an allowable range for the PCM to adjust fuel trims. If trims venture beyond those limits, the CEL sets. In general, it's +/- 25%.