Hello. I just bought a 2004 Mustang Mach 1 and the car will idle at 600-650 rpm's and then go down to around 200 and die. I have cleaned my IAC and it does the same thing, can anyone help me out? Thanks.
The PCM maintains two idle trim settings. AC on and AC off. This symptom usually has three causes.
1 - AC is low on Freon and is short cycling. If the AC is short cycling, it is not running long enough to allow the PCM to re-learn new AC on idle trim values. Either fix the AC or jump the AC low pressure switch to force the AC to run for several minutes.
2 - IAC is not really functioning. Often the IAC will quit functioning for various reasons. PPL will adjust the TB throttle idle set screw in an attempt to solve an idle issue. Problem is this manual method works for certain temperatures and AC off. Low idle is the result with the AC on. Perform the IAC basic functionality tests called for in the following post.
Thanks brothers. I took the car to a good mechanic and he told me it was the IAC, so I bought one at advanced auto for 68.00 Hope this fixes the problem. Thanks again.
I think I have this same problem. With it running rough at idle and dying when I turn the ac on. Also when I'm driving and shift to second and it gets to about 2200 RPM and higher it starts to jerk badly no to little throttle response. Also the trans feels like its burning up. It heats up the inside of the car and the shifter gets overly hot.
Well I found out today the guy who had it tuned and didn't have cats on it and the Dealer put cats on it before I bought it. Basically w the tune and Headers the cats started burning up and screwed up the computer and made it act that way. Took the cats off and it ran perfect. Thanks for the info!!