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The car is a 2001 fordmustang cobra svt with a 4.6L and a manual transmission. First off, I am a mechanic. Also I have an autel scan tool. So my problem is when cold this car starts and immediately dies. If I keep my foot on the gas it runs fine. Once its warm it idles fine. With my autel dont give me anything to go on, tps, air flow, map coolant sensor, everything looks good. About the only thing the autel gives me is long term fuel trim is at -5 meaning its running rich. Hooked up a fuel pressure gauge as see thefuel pressure fluctuates between 28 and 32 psi. If I unplug the fuel pressure regulator the fuel pressure should increase but the pressure drops to 20 psi. Other random observations may or may not be relevant it appears that the head gasket on the left side as well as 1 of the freeze plugs appears to be seeping and the oil pressure sender is leaking, but oil level is fine. Car has 90k miles. Any thoughts on where to go from here would be appreciated. Thanks.
 

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Check for vacuum leaks at inlet manifold gasket and on cracks in PCV metal pipes and parts that may close up when warm.



The plastic intake manifold can also crack in various places and close up like metal when warm. While they more commonly cause coolant leaks they can also cause vacuum leaks especially if an aftermarket replacement manifold has been fitted and not correctly torqued up. The manifold nuts on aftermarket replacement manifolds can also come loose creating vacuum leaks at the gasket.

see http://www.agcoauto.com/content/news/p2_articleid/185


Note: I don't think I have ever actually worked on one of these engines as they are uncommon grey imports in Australia but these symptoms in a generic sense do suggest a vacuum leak that closes up when the engine is warm.
 

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Check for vacuum leaks at inlet manifold gasket and on cracks in PCV metal pipes and parts that may close up when warm.



The plastic intake manifold can also crack in various places and close up like metal when warm. While they more commonly cause coolant leaks they can also cause vacuum leaks especially if an aftermarket replacement manifold has been fitted and not correctly torqued up. The manifold nuts on aftermarket replacement manifolds can also come loose creating vacuum leaks at the gasket.


see http://www.agcoauto.com/content/news/p2_articleid/185


Note: I don't think I have ever actually worked on one of these engines as they are uncommon grey imports in Australia but these symptoms in a generic sense do suggest a vacuum leak that closes up when the engine is warm.
@

But.... a vacuum leak will make it run lean, and I am running rich. This is leaning on a not enough air... maybe a dead rat in the air filter... lol
 

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But.... a vacuum leak will make it run lean, and I am running rich. This is leaning on a not enough air... maybe a dead rat in the air filter... lol
Not on a computer controlled car; the sensors will often detect the additional air/lean mix from the vacuum leak and try and adjust by enriching the mixture. Especially so at cold idle. One of the joys of modern computer controlled motors is often the computer in response to input from sensors will adjust mixture and timing to counter such faults producing contrary codes and behaviours. This is For example a vacuum leak at on inlet port will mean the O2 sensor will detect a lean mixture but as there is only one O2 sensor on each exhaust bank the PCM doesn't know which cylinder has the issue and the PCM will then enrich the mixture on all ports on that bank leading to it then outputting a rich code.

BTW for similar reasons, using fast start and other aerosols, gas, oil etc will often not detect the vacuum leak; the PCW simply adjusts the mixture and timing too quickly to pick up any change in response to what is sucked in. You have to resort to smoke tests (smoke machine or the cheaper but unhealthier cigar method) or getting a meter or so length of windscreen washer sized tubing and puting one end in your ear while poking around the inlet manifold listening for a sucking noise at hot and cold idle.
 

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Faulty iac's can do this. Have you checked the ect sensor?
 
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