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

Starting/Idling problems??

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Old Aug 19, 2012 | 01:57 PM
  #1  
Doyon's Avatar
Doyon
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From: Alaska
Default Starting/Idling problems??

In the past couple of days I've noticed it takes maybe a second long (if that) to start the engine when turning the key.

The past few days (before last night) were 104 and 102 degrees (I don't know if weather will change anything) and last night was about 75ish with thunder and lighting. On the way home from a friends house around 130AM I stopped at a stop sign and a stop light with normal idling then on the third stop light it idled really low then died, but started back up no problem, it did this a couple of times so I gave it some gas.

Finally got onto the highway and stopped a couple more times (after exiting) with ZERO problems, nothing unusual.

Any thoughts on what it could be? I had a guy at all batteries take a look at the battery about a month ago and he said it looked fairly new, so I don't know if my battery as anything to do with it...
Old Aug 19, 2012 | 07:48 PM
  #2  
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cliffyk
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From: Saint Augustine, FL
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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;

  • You can check the IAC with a multi-meter, unplug the electrical connector and measure the resistance between the two terminals, it should be 6Ω to 13Ω--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 10kΩ--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 12.0V or more--if not you have a wiring problem.

It cannot be a fuse issue as the IAC, all the injectors, the MAF, and two PCM reference voltages are all supplied by the same fuse--I.e. the engine would not run if that fuse were blown...

You should be able to get a new IAC at any FLAPS for $90 or less...
Old Aug 19, 2012 | 08:08 PM
  #3  
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Doyon
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From: Alaska
Default

Okay i'll have a look at this tonight. Drove the car today with zero problems also, but will still check. Thanks a lot Cliff.
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