Car wants to die with heat on? -

4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

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Old 11-13-2012, 11:14 AM   #1
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Location: Alaska
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Default Car wants to die with heat on?

I've recently encountered a problem with my heat... When I have the heat on, no matter how high or low, if I come to a stop, it normally wants to die. It'll jump from around 600rpm to 1200rpm down to 200rpm to around 500rpm then die. Of course it doesn't do that exactly every time, but it's roughly like that each time. I can give it gas and it will not die, but that gets old haha.

Any thoughts?

Thanks guys!

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Old 11-13-2012, 04:28 PM   #2
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Try replacing your iac. Mines just went bad yesterday and when I was turning on the ac the rpms were dropping down super low and I was doing the sane thing you were doing. Ether that or it could be in the time if you had a custom tune done.
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Old 11-14-2012, 09:12 AM   #3
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99.44% of the time problems such as you describe are a failing/failed Idle Air Control (IAC) valve.

Here is how it can be tested:
  • With the engine warm and idling disconnect the IAC electrical connector, the engine rpm should drop significantly or even stall--if it doesn't the IAC is bad buy a new one -or- it could be that the throttle stop screw is not properly set, click here to see how to do this;

  • You can check the IAC with a multi-meter, unplug the electrical connector and measure the resistance between the two terminals, it should be 6 to 13 Ω--if it isn't the IAC is bad, buy a new one;

  • Next check the resistance between each terminal and the IAC body, in both cases it should be better than 10 kΩ--if it is less the IAC is bad, buy a new one;

You can also check the voltage between the red wire at the IAC (connector plugged in, key on engine off (KOEO) and ground (the IAC body will work), it should be 12.0 V or more--if not you have a wiring problem...

You should be able to get a new IAC at any FLAPS for $90 or less...
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