Taciturn

I've been puzzled for over a week now as to what my car has been doing. my Automatic 96 GT with 93k miles on it just recently, on a long trip back from my Christmas vacation (approx. 12 hours) decided that it would idle at 1500 rpm when in either Park or Neutral, and in any of the driving gears idle at around 1000-1100. It transitions hard from park into first, but that may be due to the higher rpms. When you let off the gas and let it creep forward, it will climb its own way to 1500 rpm. It drives normally at highway speed. The code being thrown is 1506, faulty IAC, but I replaced that personally only a couple of months ago.

All of the gaskets on the TB and Plenum, as well as all the vacuum hoses I can see atop the motor are properly sealed, and were recently replaced. Could this be my TPS? PCV valve? a vacuum leak at my Intake Manifold? Any input or previous experience would help me immensely. If you need me to go out and disconnect various components to try and produce a result, I can, just let me know.

I'm really trying to sell my car, and until this is right, I can't. Thanks in advance.

tadpole1969

may need to try and clean the mf sensor or get a new one also
That code is set when the idle speed(RPM) of the motor is consistently higher than the desired idle RPM. It is almost always IAC or vacuum leak related

TXMach

It just started randomly? Or, did it happen after you did some work? It could be caused by any one, or a combination of any of the aforementioned components.