I need help please, I have a 2004 mustang GT. I recently replaced the idle air control due to my car constantly dying. That sorta fixed the issue, now when I when I come to a stop and slow down it idles around 2 grand before dropping down to around 300 rpm's and finally it shoots back up to around 800 rpm's. Sometimes the car does completely die but will restart right back up. I've replaced all hoses, PCV valve and Idle Air Control. Car has been hooked up to diagnostic machines and it doesn't read anything is wrong with the card. Any ideas?

 

i would check your tps, you can test it with a multimeter and check your mass air flow + you may need to clean or replace your egr valve, it may be clogged up

 

Sounds like you got a bad IAC, and it is not uncommon to get it that way from the part store this is one of those parts you want OEM Motorcraft

JMO

 

Did you replace your IAC or clean it? Cleaning works for some...and it is sometimes just a temporary fix. Did you mess with your TPS some how?

 

This is exactly what both of my 2000 gts did when the front 02 sensors start to go bad.