Today on the way home from the car audio shop, the Check Engine Light came on. Great.

Stopped at O'reillys and borrowed their code reader. It tells me I'm running lean>? I'm inclined to believe this, because the last few weeks the car does feel like it has less power.
The guy at O'rellys said "It could be a lot of things... clogged injectors, a dirty O2 sensor" He suggested taking the O2 sensor out and cleaning it.

Other than the "You need a tune for a Cold air kit" answer, what else should I be looking at?
Ok, I have some type of Cold air filter on the stang, and a magnaflow exhaust, but both of those items have been on for over a year without causing a code.

How much fun is it going to be to take out the O2 sensor from the exhaust?

 

It should be pretty straight forward, espcially if you have a lift. Just let it set till its nice and cool and I mean cool cause those cats get hot and stay that way for a while.

As long as you dont have any rust issues which you shouldnt they should just come right out with the twist of the wrench. Then just unplug and plug the new ones in and screw them back in. I believe there are just two on these cars to, its been a while since I looked but that makes it that much easyer since you dont have more than that to contend with

My friends 04 has 4 of them and the top two are hussys but these cars were made for service work like this

 

What code reader? How did it determine the "running lean" condition?
What was the actual DTC #.
Going on the word of someone who wants to sell you something is just wrong.
Parts stores love the diagnosing of problems with a 'code reader' and then throw parts at the
problem until it disappears. Has he determined which O2 sensor is bad ( there are more than 1).
Get the DTC # and diagnose it the Ford way...

Cant go wrong there.

I would of course go thru the entire air intake system and look for leaks
or something that the 'car audio guys' knocked off or something.
This lean thing (if that is what it is) happened right after they forked with
your stang?

 

Make sure your intake is on tightly. Get the codes read again and get the actual #. If its one bank running lean you can narrow it down alot.

 

what CAI do you have installed?

 

A no-tune-required CAI can run on the ragged edge of throwing a CEL for some time before a change in ambient temperature, humidity, barometric pressure, disturbances in the space-time continuoum or whatever kicks it over the edge. Instruments drift... Numerous possibilities.

If it persists, reinstall your stock airbox (the CAI isn't doing much other than look pretty w/o a tune anyway) and see if you still get the CEL.

 

1 year later. It's cold outside and the code is back. Hmm...

 

But what code is it??
A code is not a code is not a code...

 

sounds like the cai doesn't like the cold air. As mentioned, the no-tune-required ones usually runa little lean. If the cold temps outside caused it last year it makes sense that is what caused it this year. Get the code number and use the link 157dB supplied above.

 

My money is on the CAI. Non-tuned CAI's; I hate 'em with a passion.