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Old 12-13-2014, 04:04 PM   #1
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Hanging idle problem on 2002 mustang gt

Hey guys I know this is a question that I'm sure many of you have heard about before my thread but I've had a hanging idle problem ever since I bought my car. Seems like when I clutch and pull out of gear it wants to stay around 2 grand on the rpms for about 4-5 seconds before it falls off back to normal idle. Didn't know where to start to take care of this problem. Any help would be great. thanks.


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Old 12-13-2014, 04:17 PM   #2
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I would look into the idle air control valve. (IAC). Many say you can clean it, but Ford claims it's not "cleanable". I guess it doesn't hurt to pop it off and make sure there is nothing solid inside keeping it from working. Make sure you try and keep from boogering up the gasket.
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Old 12-13-2014, 04:22 PM   #3
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I cleaned out my throttle body, plenum and tried to clean the IAC although it's hard to clean the IAC due to how it's made. And that didn't change anything. But I will say on my gasket the left side of the gasket where the Dumby hole is torn and a decent chunk is missing. But being over the dumby hole I wouldn't think it would keep it from sealing. And I can't hear a leak. But then again the leak might not be horrible just bad enough to throw my idle off.


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Old 12-13-2014, 04:46 PM   #4
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The computer is programmed to hold a higher than normal idle while the car is rolling. This is so that the Hydroboost system, which is the power assist for the brakes, has enough power for braking and power steering.
2000 RPM's is a bit high though. It probably is your IAC. Cleaning them typically does nothing because they are usually worn out by the time that they get dirty enough that they need to be cleaned.
If you do determine that the IAC needs to be replaced, I recommend purchasing one that is manufactured by either Motorcraft or Hitachi as the other makes seem to be very troublesome.
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Old 12-13-2014, 04:54 PM   #5
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IAC delete. The throttle response will be exact. no ECU bull ****. ecus are gay.
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Old 12-13-2014, 05:02 PM   #6
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You can't delete the IAC. There is, however, an IAC mod that makes the idle drop faster.
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Old 12-13-2014, 05:43 PM   #7
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IAC delete. The throttle response will be exact. no ECU bull ****. ecus are gay.

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Old 12-13-2014, 05:44 PM   #8
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oh okay. idk why I thought somebody mentioned a delete. I was high on marijuana cigarettes when I read that thread though lol
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Old 12-13-2014, 06:01 PM   #9
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Lol.
You were probably thinking of the EGR delete.
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Old 12-14-2014, 12:29 PM   #10
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Dont buy a iac from an autoparts store. They are usually crap. Order a hitachi or get one through ford. Oem was hitachi and one other brand. One is longer than the other, but both work.

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Old 12-22-2014, 03:56 AM   #11
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On my buddys 02 it was his tps. We would give it a quick rev and it would hang ip around 1800 for a few secs then drop. His was manual if it makes any difference

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Old 05-17-2015, 12:50 PM   #12
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I have the same hanging problem.

Colt23, did changing the IAC valve fix your problem?


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Old 05-17-2015, 01:36 PM   #13
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I used to have that same hanging idle problem with my car.. You know.. Back when I had EFI lmao. rookie mistake. LIterally not one single fuel system related issue since I switched to carb. No drop in MPG and a noticeable increase in horsepower... Just saying
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Old 05-17-2015, 02:36 PM   #14
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I would first replace your IAC valve. No cleaning it b.s. If your problem isn't solved I would look into your charging system. If you had parasitic draw (even a small one) that could be causing your PCM to go through a idle relearn. As it goes ford pcms are hyper sensitive to low battery voltage. So a battery at the end of it's life so a weak alternator can also be the cause.


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Old 05-17-2015, 06:29 PM   #15
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I used to have that same hanging idle problem with my car.. You know.. Back when I had EFI lmao. rookie mistake. LIterally not one single fuel system related issue since I switched to carb. No drop in MPG and a noticeable increase in horsepower... Just saying
Soo you'd rather spend $200+ to swap a carb on instead of $50 to replace an IAC valve?
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Old 05-17-2015, 07:10 PM   #16
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Soo you'd rather spend $200+ to swap a carb on instead of $50 to replace an IAC valve?

Flawless logic isn't it...


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Old 05-17-2015, 07:38 PM   #17
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Soo you'd rather spend $200+ to swap a carb on instead of $50 to replace an IAC valve?
And solve PATS problem, expensive fuel pump replacements down the road, ECU problems, fuel pump relay problems, and every other EFI problem that you guys CONSTANTLY are posting frustrating threads about. All that **** is gone for good.

By the way, it was only $150 to swap to a 4 barrel carb.
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Old 05-17-2015, 07:40 PM   #18
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Flawless logic isn't it...


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SCroll through the forum some time and look at all of the EFI and ECU related problem threads. And then think to yourself "I wonder if Panther deals with this plethora of fuel-system problems" The answer is No way in hell.
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Old 05-17-2015, 07:50 PM   #19
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You're missing one very important circumstance, I don't care. If there's an issue fix it. If man makes it, it can break. It's that simple.


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Old 05-17-2015, 07:57 PM   #20
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You're missing one very important circumstance, I don't care. If there's an issue fix it. If man makes it, it can break. It's that simple.


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Issue = EFI is dumb as **** and leaves you stranded all the time
Cure = Get rid of dumb *** EFI and put something on there that is significantly less complex and expensive

I did fix it
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Old 05-17-2015, 08:05 PM   #21
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Well it was quiet and peaceful for a little while... Now we have to hear about unrelated things and swapping to carbs again.


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Old 05-17-2015, 08:08 PM   #22
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Lovely isn't it...


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Old 05-18-2015, 07:46 AM   #23
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oh. i was gettin ready to post that the only correlation ive found with the hanging idle was when my a/c wasnt fully charged.
sounds weird, but basically, as the clutch would engage and disengage at a stop light, my rpms would bounce between like 900 rpm and 700 rpm (clutch engaged vs disengaged, respectively). after it would do that, the ecu would act like it was having an idle problem, and thats when it would start hanging rpms. An ecu reset always fixed the issue. then charging my a/c allowed the rpms to jump to 900 or so when the clutch engages, then slowly work its way back down to normal idl, and stay that way since the clutch stays engaged.
I havent heard anyone make that connection before, so i have no idea if its the same for anyone else with a hanging idle. but i kinda feel that in my case, its the ecu attempting to correct something, more than a failing IAC. (havent changed mine, and its working find nowdays.)
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Old 05-18-2015, 07:53 AM   #24
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^ that's interesting,


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Old 05-18-2015, 09:15 AM   #25
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I used to have that same hanging idle problem with my car.. You know.. Back when I had EFI lmao. rookie mistake. LIterally not one single fuel system related issue since I switched to carb. No drop in MPG and a noticeable increase in horsepower... Just saying
You're turning into the carburated troll
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Old 05-18-2015, 10:06 AM   #26
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You're turning into the carburated troll

If we don't pay attention to it, it may go away.


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Old 05-18-2015, 10:16 AM   #27
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I doubt it. I've got 3 carb cars. I'm not seeing how they are so much better. But to each his own I suppose.


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Old 05-18-2015, 11:17 AM   #28
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If we don't pay attention to it, it may go away.


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Lol, we can only hope.
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Old 05-18-2015, 05:09 PM   #29
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I doubt it. I've got 3 carb cars. I'm not seeing how they are so much better. But to each his own I suppose.


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Correct.

Some have a strong dislike for EFI, and others have no love for BMW's...

To each their own.
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Old 05-18-2015, 09:23 PM   #30
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Today, I read a post explaining that cars built since 2000 +/- have 'hanging' programmed in the ECU. The idea is that a rapid engine RPM decline spews the worst gasses into the atmosphere. Hanging slows that RPM decline and burns gas better. Generally, cars with automatic transmissions don't have this programming.

The hanging is different than a bouncing idle. Hanging usually occurs when shifting gears with a MT. The engine RPM may rise a little in a bad shift. The engine RPM, then, declines slowly when you first release the gas pedal. Changing the IAC valve should have no bearing on a hanging RPM.

About two years ago, I noticed my engine hanging a couple of weeks after changing COPs to some aftermarket brand. (They actually work better than the DG508's I'm determining as of today.)

Last week, I purchased and installed new DENSO boots/springs for the old FOMOCO COPs and the engine still hangs. I'm not sure how I did not notice the hanging when I first bought the car (GT-Manual) over two years ago.

I believe there is more to this hanging issue and would really like to resolve it.


To the carburated guy writing posts: Good for you! I'm certainly impressed!!
To the knuckleheads slamming the carburated guy, please be quiet. The rest of us are trying to make our cars run better. "You're takin' up space" (Van Zant-2006).
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Old 05-18-2015, 09:38 PM   #31
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Hanging idle problem on 2002 mustang gt

Quote:
Originally Posted by straybullitt View Post
Correct.



Some have a strong dislike for EFI, and others have no love for BMW's...



To each their own.


Oh I like BMWs, I just don't understand why the Germans decided to ruin them. The materials they used and way it's applied. Their build quality sucks now, argue if you want I don't care. I'm tell you what I see when I work on them.


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Old 05-18-2015, 09:41 PM   #32
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Originally Posted by escottcarp View Post
Today, I read a post explaining that cars built since 2000 +/- have 'hanging' programmed in the ECU. The idea is that a rapid engine RPM decline spews the worst gasses into the atmosphere. Hanging slows that RPM decline and burns gas better. Generally, cars with automatic transmissions don't have this programming.

The hanging is different than a bouncing idle. Hanging usually occurs when shifting gears with a MT. The engine RPM may rise a little in a bad shift. The engine RPM, then, declines slowly when you first release the gas pedal. Changing the IAC valve should have no bearing on a hanging RPM.

About two years ago, I noticed my engine hanging a couple of weeks after changing COPs to some aftermarket brand. (They actually work better than the DG508's I'm determining as of today.)

Last week, I purchased and installed new DENSO boots/springs for the old FOMOCO COPs and the engine still hangs. I'm not sure how I did not notice the hanging when I first bought the car (GT-Manual) over two years ago.

I believe there is more to this hanging issue and would really like to resolve it.


To the carburated guy writing posts: Good for you! I'm certainly impressed!!
To the knuckleheads slamming the carburated guy, please be quiet. The rest of us are trying to make our cars run better. "You're takin' up space" (Van Zant-2006).

He deserves the bashing because he is a troll - elevated to a carbureted troll status. If your so stuck on the "hanging rpm's" sell your car and buy something different!

Now that I got that out, try to find a restricter plate for your IAC. There was some peeps that made some for the Mach 1 IAC's. The restricter plate would allow the rpm's to fall immediately after you got off the accelerator or put the clutch in. From the threads I've read on forums, they seem to work pretty well, but I don't want one. I could care less about hanging rpm's lol.


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Old 05-18-2015, 09:44 PM   #33
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I thought he was leaving? Made a big deal about it
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Old 05-19-2015, 01:09 AM   #34
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I thought he was leaving? Made a big deal about it
Who? Panther?

He just got back!
He's not going anywhere...
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Old 05-19-2015, 05:03 PM   #35
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SOrry for missing this flame thread. I was too busy out enjoying how my throttle actually does what I tell it to do
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