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Discussion Starter #1
i've really started to have my share of problems lately, after my first year of ownership was wonderful, but anyway...the car has never idled correctly, and now its acting weirder. when i shift into neutral, clutch pedal up and am coasting to a stop sign or red light the revs still jump around on occasion from 800 to almost 2000 sometimes. once the car comes to a stop it settles back down to 750 and stays there. now it idles at like 1000 and i hear a strange whirring sound when i take off in first, from idle to about 2000 rpm, then shift to second and it happens again. idk what it is, i cleaned the mass air flow sensor, and sprayed the throttle body with carb cleaner too. no idea whats going on???

thanks
ben
 

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My 2005 has the same problem when coasting to a stop not sure what it is but it doesnt always do it.
 

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Discussion Starter #3
yea, mine doesn't always do it either. idk what it is though and its annoying
 

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i think you can rule out a vacuum leak. if that was happening, first off it would run rough all the time, and or it would die down, not rev up. when its running, pop the hose clamp loose on the pcv valve, it will die fast if you pull it off, but just loose, you`ll get a idea.

my car revs up and down maybe even a few times when i start it up cold, when its cold out till it gets warmed up a little and the idle comes down. i think its from the race tune i have. but then it doesnt do it again. i dont have a handle on what exactly is causing it to do that though.
 

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Discussion Starter #5
yes, when its cold and i start it the revs hangout at about 1300 or so, and eventually sinks back down to 800. only when im out on the road, or sitting at a light does it act strange, im told the plastic intake manifold can leak from the bottom? could that cause it?
 

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Discussion Starter #6
does anyone know?
 

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make sure you have motorcraft plugs and they are in good working order.
Fords are very particular on the spark plugs
and your MAFS maybe dirty so check your air filter too
good luck
 

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Discussion Starter #8
i cleaned the mass air flow sensor, and sprayed the throttle body with carb cleaner too. no idea whats going on???
i did clean it, and would the plugs really affect this? because the engine doesn't miss a beat under load or at normal 800 rpm idle, no misfires...
 

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i did clean it, and would the plugs really affect this? because the engine doesn't miss a beat under load or at normal 800 rpm idle, no misfires...
I am concern about the weather there... meaning, I wonder over the years/ miliage being in a climate where its freezing cold then really hot. Over time this can cause the air intake to become more brittle and can lead to a small air leak in the air intake manifold. I had this problem on a 96 GT years ago. I wouldn't doubt it, you having the same problem. I had all the issues that you have and as time went on, I wasn't firing on all cyclinders. Firestone (yeah, why I went there) said I had a head gasket leak. I knew it wasn't that. I went to another place and they showed me a small cracked in the manifold. I replaced it want till this day, it work perfect.

also, do not powder coat the manifold, it cannot take the heat to treat the paint and this also will cause it to fail.
 

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Discussion Starter #10
you really think so? because thats the best sounding answer i've gotten from anyone thus far, what should i do? take the manifold off?
 

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you really think so? because thats the best sounding answer i've gotten from anyone thus far, what should i do? take the manifold off?
Well, its possible... if you are comfortble with removing it and inspecting it.

If you want to, buy a pre owned air intake manifold that is in good condition and swap it out to see. THey are pretty cheap on ebay.

In my OWN opinion... I would swap it out, just to see what happens. So far everything points to an air leak.. just have to figure where its coming from.
 

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Discussion Starter #12
could it be just a gasket leak? maybe its not torqued down properly? sorry i have so many questions i am just unfamiliar with this kinda stuff.

thanks
 

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I have a 06 which has idle varying problems also. I also have CEL engine runs lean codes. I took it to Ford but they never could figure it out either. I' m leaning toward replacing the intake manifold gaskets myself. They're just rubber o rings. This is a good thread.
 

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Discussion Starter #14
im just afraid im gunna mess something up, the problem isn't always there, but it does bother me.....has anyone solved this problem? trial and error
 

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could it be just a gasket leak? maybe its not torqued down properly? sorry i have so many questions i am just unfamiliar with this kinda stuff.

thanks
You know, I wouldn't rule out the gasket leaking, its possible... but i don't think so. Its possible if you torqued it down to much you will crack the manifold. Its just plastic/composite. They are not meant to run for ever... but they plan on them lasting at least 100,000 miles. But things happen and things fail.

But as I said before, I would really look into replacing the maniford since its "cheaper". Just buy a used one, if you still have the same problem, you know its not the manifold. It could be in teh thorle body. But that thing is so senistive, if you had a leak there, the engine will shut off. Trust me, I played around with it. And that was from not tighting it down.
 

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Discussion Starter #16
it is possible to test for a leak? a vacuum gauge or something?
 

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Same thing...

I have the exact same issue. I can tell you it's NOT: spark plugs, MAF, air filter and throttle position sensor. I've swapped all these parts with known-good parts during other maintenance on my 'stang (which has 130k mi on it).

One interesting twist: on my car, if the idle is wandering in the high direction, you can turn off the car, turn it back on, and then everything is normal.

This makes me thing the source of the problem is one of two things:

1. The PCM is getting an incorrect initial value for air flow upon cold start-up.

2. There's a leak in the air intake system that diminishes or goes away when it's hot. (I like this one, because it would be explained by a crack in the plastic intake manifold. As the manifold heats up and expands, the crack closes a little; but the PCM is still compensating for a leak that was worse when cold.)

Dave
 

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Discussion Starter #18
I have the exact same issue. I can tell you it's NOT: spark plugs, MAF, air filter and throttle position sensor. I've swapped all these parts with known-good parts during other maintenance on my 'stang (which has 130k mi on it).

One interesting twist: on my car, if the idle is wandering in the high direction, you can turn off the car, turn it back on, and then everything is normal.

This makes me thing the source of the problem is one of two things:

1. The PCM is getting an incorrect initial value for air flow upon cold start-up.

2. There's a leak in the air intake system that diminishes or goes away when it's hot. (I like this one, because it would be explained by a crack in the plastic intake manifold. As the manifold heats up and expands, the crack closes a little; but the PCM is still compensating for a leak that was worse when cold.)

Dave
that sounds very accurate. mine does the same deal, i shut it off at a red light, fire it up again and the problem isn't as bad, idk what it is though but its starting to really annoy me, how do i fix it? new intake manifold? new gasket? no one seems to know, or have had it fixed yet.
 

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that sounds very accurate. mine does the same deal, i shut it off at a red light, fire it up again and the problem isn't as bad, idk what it is though but its starting to really annoy me, how do i fix it? new intake manifold? new gasket? no one seems to know, or have had it fixed yet.
I found a junkyard manifold with 19k miles on it. I will swap it either this weekend or next weekend depending on my work schedule. I'll let you know if it does the trick.
 

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Discussion Starter #20
sounds good to me, lemme know what happens, the guys at my local auto zone said something about an idle adjustment valve or something? but i mean, my fuel consumption is fine, i got 30 mpg last tank :)
 
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