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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 03-29-2005, 10:34 PM   #1
90Mustangfan
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Default Cold start low idle...

when ever I first start up the car when cold, it idles low(600rpm) until warmed up then It idles normal (800rpm). what could be causing this. I have cleaned just about every sensor concering this. And I dont get any codes on the Koeo test. except codes 34-egr sensor bad or something.
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Old 03-30-2005, 12:10 AM   #2
90GTRagtop
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Default RE: Cold start low idle...

Could be the IAC or a vacuum leak, but mine always idles around 600 rpm, even when it's warm. It's consistant and it controls around 600, so I don't have any problems with it.
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Old 03-30-2005, 12:33 AM   #3
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Default RE: Cold start low idle...


Quote:
ORIGINAL: 90GTRagtop

Could be the IAC or a vacuum leak, but mine always idles around 600 rpm, even when it's warm. It's consistant and it controls around 600, so I don't have any problems with it.
it should idle around 800
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Old 03-30-2005, 11:22 AM   #4
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Default RE: Cold start low idle...

sounds like u have a pretty agressive cam to me?? you could have a vac leak....?
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Old 03-30-2005, 11:41 AM   #5
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Default RE: Cold start low idle...

i have a cold start problem too but i think the problem is that i still have the stock H-pipe on there with no emission stuff on there, so i think the cats are clogged. but i have a E303 cam with 1.7 RR so that doesnt help either
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Old 04-03-2005, 03:07 AM   #6
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Default RE: Cold start low idle...

you need a custom chip if you don't have one already for your 331 stroker, but if thats not the case you have a vacuum leak, for sure, i corrested all mine when i had the same problem, at least i thought i fixed all the vacuum leaks, but it turned out my lower intake manifold was the source of the leak, problem ceased ever since.
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Old 04-03-2005, 01:36 PM   #7
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Default RE: Cold start low idle...


Quote:
ORIGINAL: 88GT40

you need a custom chip if you don't have one already for your 331 stroker, but if thats not the case you have a vacuum leak, for sure, i corrested all mine when i had the same problem, at least i thought i fixed all the vacuum leaks, but it turned out my lower intake manifold was the source of the leak, problem ceased ever since.
how do i find if i have a vaccum leak? i dont have a chip but i do hear a high pitch noise when i have the car running so i think i have a leak somewhere.
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Old 04-03-2005, 03:53 PM   #8
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Default RE: Cold start low idle...

You say you hear a whistle, so try taking a tube, like a paper towel roll or similar, and hold it to your ear. Use it to try and narrow down where the whistle is coming from. Particularly listen and look for places with a hose not connected or broken.

Another way to check for a leak is to spray lightly around a running engine in specific areas with something that will cause the engine to speed up if it gets into the intake. Ether (starting fluid) will work, but you must be very carefull as it is very flammable. Spray a cold engine as opposed to a hot one, to reduce the chance of what ever you're spaying from flaming up on you. Spray lightly in an area and wait a moment to see if it's affected. If it's not, then move to another area. If you spray an area and the engine speeds up, you've got a vacuum leak.
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Old 04-04-2005, 01:31 AM   #9
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Default RE: Cold start low idle...

wel the easiest way to check for vacuum leaks is to let the engine idle and to spray carb cleaner on all the vacuum hose ends and between the upper to lower intake manifold, and see if the idle rises in an area that you spray if it does than you have a leak, now i fixed the vacuum leaks that i found and it seemed to get worse and i determined that the lower intake manifold gasket was the problem, and that was that. but with that engine if you are using a stock computer than you need to get a chip.
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Old 04-04-2005, 01:35 AM   #10
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Default RE: Cold start low idle...

also (mustang fan) the egr valve may not be working properly and that effects your idle so that may be part of your problem.
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Old 04-04-2005, 01:35 AM
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