A couple of days sgo my check engine light came on. It is running lean.But the light only comes on after I had a wot run( not right after). I have had the light turned off and it does not come on under normal driving( or so it seems). I did a search and found that the most likely answer is the vacume line near the firewall. Also with some process of elimination-- cleaned mas sensor, hose clamp bigger vac lines and zipped tied smaller ones, new gasket on the sensor in the air inlet tube.... I then tried a little propane near the firewall, nothing happened. Any other suggestions on what may be causing my lean codes? Thanx for any input.
2000 L
65000 miles
diablo chip since 2001
valve body
4x4 tran pan
diff cover with bolts
volant air intake
2" drop shackles
complete with all avail. energy susp. bushings

 

your MAF maybe starting to go out, you mentioned that it happeded after a WOT run, when the mafs begin to go bad they can not properly measure the air entering the motor and cause it to run lean. I have seen this on several ford engines that I have worked on - first just an occasional CEL then to a steady CEL untill I replaced the MAF. At WOT you can max out the MAF and cause engine damage from going lean(just run a search for blown engines) yours is a 2000 with the small MAF to start with, if it is failing you could easily damage an engine by going WOT. You seem to have went through everything else.
below are some ideas

1. Change fuel filter
2. Check Fuel Pressure 30-35 psi idle
3. Check Hi/Lo fuel pump relay
4. Check fuel pump resistor
5. Check the 'y' in the fuel tank ( doesn't sound like your issue)

if all of these check out to be good I would replace the MAF.

just my $.02

 

My "L" is still purring. No rough idle,and makes my wife feel like she is going to loose her lunch in the passenger seat when I put the "peddle to the metal".
The first thing I did, was change the fuel filter. The maf still looked a little dirty even after I cleaned it.
I have reset the computer a few times and it seems to come on more often, just under normal conditions. Thanx for input