I have a 2006 mustang GT with no mods. I have a K&N filter, and have had to replace the battery.
I recharged the filter3 months ago, and for acouple of days it threw the CEL. BeforeI could get it checked out the light went away, so I assumed thatIput too much oil on the filter, the MAF sensor got dirty, and it turned on the light.
End ofMayI replaced the battery, and now the car "surges" at idle from 500 to 750 RPM. It also dies sometimes after driving on a highway when I get to a stop.
I am in the extended warranty, and would like to avoid paying the deductible, so if any of you have any ideas,I would greatly appreciate it.
Last night I removed the MAF and it looked clean btw.

FIX- Cleaned filter, airbox duct MAF and Throttle Body. problems solved Thanks to all for their knowledge and advice.

 

i would start the troubleshooting process, by
making sure all of the physical connections in
the engine bay are sound.

1) reseat the appropriate connectors ie. maf, tps etc.
2) check all vacuum lines

after that i'd start looking toward:
maf (clean with appropriate spray)
fuel delivery (filter, injectors)
spark (C.O.P's, plugs)

 

I forgot to mention that the idle smoothes out at 750 andseems to run finewhen I turn off the A/C.

What is the proper spray for the MAF?

I have looked in the engine and made sure the connectors were connected, but could not find any obvious vacuum lines. I am concerned thatI knockedsomethingloose on the battery install, but I can't find anything obvious.

 

I sprayed mine with brake cleaner, but that's probably not the correct cleaner to use. Check your local auto parts store for something specifically for electronics. My theory was that anything designed to remove oil and evaporated quickly without leaving a residue would work, but i've been wrong before so.

 

You are VERY lucky my friend. I've seen a few people try this and about 75% of the time, it ruins the MAF.

Electronics cleaner should work, but there is a company that just released something specifically to clean MAF's. Unfortunately, I forget who it is. I wanna say CRC, but that could be wrong. I would hunt this stuff down and use that.

 

Better check even the TB cleaner to make sure it's ok to use. It's my understanding that Ford's TB's have a special coating that a non-compatibleTB cleaner may remove.

 

here's what you are refering to.

http://www.crcindustries.com/files/M...heet%20Web.pdf

I haven't had to use it yet, however, I'm always skeptical about horsepower claims in an aerosol can! I can say that I have used their other electronic cleaners and they work well.

 

I cleaned the MAF with electronic "Contact Cleaner" at lunch and now it idles about 550~650 (est) with surges to 750~800

It is CRC MAF Cleaner,going to get some after work. Fuel filter is a little old 20K mi, but wouldn't that cause more problems as more power was produced? My problem is at idle with the a/c on. thanks to all who have responded,I appreciate it and will update as I get an answer.

 

Well, at the Ford I work at, we use brake clean for MAFs all the time; in fact, that is all we use for them, just be sure to not touch the resistor as they break easily.For thethrottle bodies, Ford says not to clean them because they are not SUPPOSED to get dirty, but in reality, we all know they do. Clean them with brake clean and a stiff pipe cleaner...unless you wanna go the Ford way and purchase a new one. As far as the stalling at a stop off a freeway that is most likelya throttle body or IAC issue. NowI am not saying togo throw an IAC at it and it will be trouble free, but it is just a thought. And hammeron is correct on the vac lines about surging idle as well...

 

I would disconnect the battery again. Give it a sec, then reconnect the battery. It takes a bit for the computer to relearn the program. Same as rebooting your home computer. Start the car and take it for a short drive to relearn the program. See if that helps any..