Air/Fuel Issues

Fuel filter, really cheap to try, and should be done anyways.

Ray@VSK said:

K how about this, I remove my air filter & I start running rich but when I put my air filter back on I'm lean, during this time I was running rich IT threw up 2 codes 67 & 68 ?

Click to expand...

67...MLP sensor out of range (E4OD)
Neutral safety circuit failure.
A/C circuit was on during self test.

68...Transmission Oil Temperature Switch failed open

I see you have a 5-speed. These two are automatic transmission codes. Your computer wouldn't happen to be a A9P, instead of a A9L, would it?

Assuming all of your sensors are functioning properly...which we can't, especially the MAF and O2 sensors (which is often the culprit with AFR problems), then I'd definitely consider having the computer recalibrated for your mods. Simply having a "calibrated" MAF does not mean that your combo is going to run well. Your ECU is still calibrated for 19# injectors, stock heads, intake, exhaust, emissions, etc. The stock ECU's adaptive control can only compensate so much for certain mods and may even "fight" your attempts to tune out AFR problems with your timing and fuel pressure adjustments.

http://www.mustangworks.com/articles/electronics/InductionBlues.htm Try this article.

How did you determine that it was running lean?

So, I'm assuming the vehicle was running when you were pulling the air filter off and putting it back on...correct? Let me ask this. Is your MAF protected from the fan blowing air past it? (For example, a shield, air box, or inner fender well mount) Even Pro-M's site suggests that the meter should be protected from "fan wash" as it creates significant "noise" near the meter which may result all sorts of tuning issues. The fact that the engine runs different with and without the filter suggests your MAF may be experiencing something similar. http://www.pro-flow.com/tech info/troubleshoot.htm

Another thought. How's the electrical grounding? Is it sufficient? Electrical noise and excessive voltage drop from inadequate grounding can create all sorts of tuning problems, as well. http://www.stangtuning.com/showthread.php?t=1656

If it is none of the above, then it just may be a EEC calibration issue...and there is nothing you can do to tune it out...at least in the long term, except to have the computer recalibrated for your mods. As said earlier, just because you have a MAF that is "calibrated" for your larger injectors does not mean that the car will run well. It'll let you get the car up and running, but the job is not finished...not by a long run.