I have a Sonic Blue '05 GT with silver stripes, it is bone stock except for a K&N air filter and IMCO extreme racing mufflers. The problem I am having started before I put the mufflers on however. When my car isn't warmed up properly (whcih it seems to take a few miles on the highways to do so) it seems like it is going to die occasionally. The normal idle is abbout 900-950 rpm's and it drops to around 500, but only for a second. Then it is back to normal... It does this when I push in my clutch to coast, or stop at stop signs, etc... Any ideas? or is this normal for the new mustangs?

 

Nope. Not normal. Seems like I vaguely remember a TSB out for somethihng similiar. I could be wrong though. Maybe dig through the tech section and check out the TSBs. Or....just take it back to the dealer. That is what a warranty is for.

 

you said you have an intake. Have you re-tuned the computer yet. It may be playing tricks on your system.

 

I can almost guarantee that if you have made any change to your exhaust or intake you are going to have problems until the computer relearns the air/fuel. (it takes about 15 minutes for the computer to relearn when you restart the car) The only way to make her run good everytime after you have made a change like this is to use a reflash device like a diablo. Our little 281's are very very sensitive. You HAVE to reprogram everytime you make an adjustment to get the best possible performance out of her. After that its always best to do a dyno tune as well and you will get every last drop of power that you can squeeze out of her and the computer won't have to relearn everytime you restart.
Best of luck

 

One way to find out if it is the air filter is to put it back in and see if it goes away. If it goes away, then you need a tune before you put back the K&N. I didn't have any problems with mine when I put on my Powerflo's and when I put the CAI on, I tuned the car and so far so good. When you put the K&N on, did you remove the factory air box or is the K&N the same shape a the OEM air filter?

 

I've had the same idle surge problem as of recently not to mention that the car has gone into failsafe mode several times. I checked the codes and if I remember correctly it mentioned something about the throttlebody so its off to the dealer before long to get it checked out..One question though ..Before installing the factory tune, should I clear the trouble codes? Already cleared them once but its done the fail safe mode 3 times since. Oh yeah, forgot to mention that when it goes into failsafe mode, usually all I have to do is turn the car off and restart for it to go back to normal or as normal as possible with the surge.

 

that is what mine is doing now... taking it to the dealer soon