Check engine light
 

I got a code for lean air/fuel mixture cant remember which bank, any ideas on the cause? 98 mustang GT 4.6 SOHC

Do you have original air cleaner or after market ? And do you know also if you car has an MAF (Mass Air Flow ) sensor ?

Its a cold air intake, i dont know what brand the filter is but i do have a MAF just before the cone. It does seem to be after market though.

What happened to me after I took out all my injectors etc was my MAF sensor got dirty , I think because I had a K&N air cleaner & most reusable have to be oiled just a smidge & if any of that oil travels throught the air system the MAF sensor has 2 hair size platinum wires in it, I understand that it measures air to tell the computer how much to mix with fuel. There are two screws & a clip that holds it in place, I took mine out & used a specific spray cleaner only ! No Q tips or nothing else these are expensive parts. Isprayed waved it dry & did it again let dry reintalled & my problem went away. So they make an MAF cleaner just for this. My xwifes guy had just bought an 07 Explorer he had the same issue , I cleaned his & it fixed it , but he did not have any after market air boxes , so I'm thinking environmental changes may do it to

This is what I found here at an auto store , Do Not use break fluid or anything else.

Not pertinent but I have an SCT tuner I plugged it in & got a whole bunch of error codes , the first one was the same as yours

I really apreciate the help bro, i really love my mustang and i wanna keep her running perfect. I'll try that cleaner for my MAF and let you know what happens. I feel like crap having to ask others for help because i know how to do other stuff like rebuild an engine but that code just really got me stumped.

Don't feel that way at all , I myself can do a lot with older engines but these new high tech I'm at a loss , I often learn from others or figure it out , but if I can't I won't do it.
Just like having an SCT with 3 different engine tunes, I read someone took their car in for service, they reflashed the cars ECM electrinic control module & didn't tell the cars owner , so when they got car back he plugged in the tuner & forgot to read the strategy code from ECM to make sure it matched , he didn't so it screwed his cars pc had to have it towed in so Ford could reprogram a few hundred $ so if you have one always read that number and return to factory tune before taking in for service. I always make a point to say leave it alone , if you have to call me to explain why , because then i have ro get Tuner redone if so.

Hey there a TacoBill's how to link here in 05-09 gt performance mods I think , excellect reads

I tried that cleaner and it didnt work, i dont know what else could cause that code.

Have you ever had your spark plugs out ? You don't want them in too long & if you did , did you use anti sieze for them so they dont loosen by them selves ? Try checking plugs . Then after disconnect ground to reset computer & see if error returns.

I did tune up last year and i did use anti-seize. When i come to a stop or tap the gas in neutral the rpms will go up for a little bit then drop down almost stall then pick up over a grand then come back down to maybe 400 for arguments sake then idle back at 800-900

Usually the idle symptom is resolved with cleaning the throttle body from what I've read.
As for the code, I assume with a CAI you have a tune? Have you reloaded the tune?
Have you checked to see the plugs are still tight? Seems like the 4.6L 2v has issues with plugs working their way out.
Something is letting too much air into the combustion chamber - either the tune is faulty, or something mechanical. Is the intake manifold tight? Injectors a possibility? How about the O2 sensor failing? Or is the code cylinder specific?

I didnt mess with the computer at all. The code isnt cylinder specific.

I dont know what a CAI is

Cold air intake

Could just be an O2 sensor going bad

I have a leak before the cat.