different idle during crusing 2005 Mustang GT - Ford Mustang Forum
 
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post #1 of 15 (permalink) Old 03-30-2010 Thread Starter
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different idle during crusing 2005 Mustang GT

this may not be a problem but it is something thats been bothering me...

wile at any speed over 3mph (about 3, its hard to judge exactly when) the engine idles at around 1000 RPM. this is easily noticed when shifting gears and the clutch is just held in and RPM's allowed to decline to idle. they will never drop down to what my normal idle is, around 780. im wondering if anyone else has this same symptom. im also wondering if this is something that can be changed in a tune, like a neutral RPM/ drive RPM. (i have noticed this in my tuner and changed the drive idle to no effect).


2005 Mustang GT
Paxton Novie 1200SL, Comp NSR Blower Grind 2, MMR Shortblock, C&L 95mm Mass/Air sensor, 39lb injectors, Motoblue ignition coils, Motoblue throttle plate spacer, Borla XR-1 Long Tube Headers and no cat x-pipe, Hooker Aero Chamber muffler, Custom LaMotta Performance tune, G-force tires, B&M shifter, Kennybell b-a-p, AEM analog A/F gauge, Interceptor scan gauge, McLeod RST clutch, aluminum flywheel
intercooler/smaller pully to come...
and yes it is my DD
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post #2 of 15 (permalink) Old 03-30-2010
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It probably just idles higher because there is less drag on it. Clutch is pushed in etc. I wouldn't worry about it.

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post #3 of 15 (permalink) Old 03-30-2010
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Adjusting idle drive does nothing for a manual transmission car. You need to adjust idle neutral.

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post #4 of 15 (permalink) Old 03-30-2010
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What your adjusting is for an automatic. And yes it should be adjustable in the tune.


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post #5 of 15 (permalink) Old 03-30-2010 Thread Starter
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i guess i have not made myself clear. it has nothing to do with more or less drag on the engine. i know the "drive" setting had nothing to do with it but i was too tempted to try. i am not having an idle problem when stopped. it is always right on and steady. as soon as the car is at any speed it begins to idle higher, always right at 1000. i have even tryed keeping the car in nuetral and pushing it down a hill to see if the rpm's will increase and they do, with absolutely no throttle input, just ground speed. you say it "should be adjustable". does this mean there is a sort of idle table that can be adjusted for different ground speeds? maybe if i tryed to take a video of what it's doing it would make more sence.

2005 Mustang GT
Paxton Novie 1200SL, Comp NSR Blower Grind 2, MMR Shortblock, C&L 95mm Mass/Air sensor, 39lb injectors, Motoblue ignition coils, Motoblue throttle plate spacer, Borla XR-1 Long Tube Headers and no cat x-pipe, Hooker Aero Chamber muffler, Custom LaMotta Performance tune, G-force tires, B&M shifter, Kennybell b-a-p, AEM analog A/F gauge, Interceptor scan gauge, McLeod RST clutch, aluminum flywheel
intercooler/smaller pully to come...
and yes it is my DD
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post #6 of 15 (permalink) Old 03-30-2010
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Quote:
Originally Posted by tltcracing View Post
i guess i have not made myself clear. it has nothing to do with more or less drag on the engine. i know the "drive" setting had nothing to do with it but i was too tempted to try. i am not having an idle problem when stopped. it is always right on and steady. as soon as the car is at any speed it begins to idle higher, always right at 1000. i have even tryed keeping the car in nuetral and pushing it down a hill to see if the rpm's will increase and they do, with absolutely no throttle input, just ground speed. you say it "should be adjustable". does this mean there is a sort of idle table that can be adjusted for different ground speeds? maybe if i tryed to take a video of what it's doing it would make more sence.
I understand now... I think they will all do this to some extent. I know when I back down my driveway in neutral the revs will remain high until I hit the bottom and come to a stop. Why?? I have no idea.

1965 Mustang Coupe
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post #7 of 15 (permalink) Old 03-30-2010
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Yup, mine does the same idle thing. I was noticing it today..... Kinda makes me wonder why it does this......

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post #8 of 15 (permalink) Old 03-30-2010 Thread Starter
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my initial instinct was that this was designed by ford to make shifts a little bit easier. instead of just dropping the RPM's, they alow them to hang somewhat to ease the clutch engagement in the next gear. now where im having problems liking this is i would like to have my RPM's drop as quickly as possible, much like a high compression motor. my car ran like that before i had my huge motor failure, but i had the car completely re-tuned since then. maybe this is a feature that can be disabled. but it makes me feel a little bit better to know that someone else experiences the same thing.

2005 Mustang GT
Paxton Novie 1200SL, Comp NSR Blower Grind 2, MMR Shortblock, C&L 95mm Mass/Air sensor, 39lb injectors, Motoblue ignition coils, Motoblue throttle plate spacer, Borla XR-1 Long Tube Headers and no cat x-pipe, Hooker Aero Chamber muffler, Custom LaMotta Performance tune, G-force tires, B&M shifter, Kennybell b-a-p, AEM analog A/F gauge, Interceptor scan gauge, McLeod RST clutch, aluminum flywheel
intercooler/smaller pully to come...
and yes it is my DD
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post #9 of 15 (permalink) Old 03-30-2010
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Quote:
Originally Posted by tltcracing View Post
my initial instinct was that this was designed by ford to make shifts a little bit easier. instead of just dropping the RPM's, they alow them to hang somewhat to ease the clutch engagement in the next gear. now where im having problems liking this is i would like to have my RPM's drop as quickly as possible, much like a high compression motor. my car ran like that before i had my huge motor failure, but i had the car completely re-tuned since then. maybe this is a feature that can be disabled. but it makes me feel a little bit better to know that someone else experiences the same thing.
You are partially correct. The revs hang to reduce stress on the drivetrain and for fuel economy.

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My guess is that this is definitely emissions related. If an engine drops too quickly from high rpm to a low idle, then too much of the wrong stuff comes out the tailpipe.
You want further details, then ask The Bureau of Automotive Repair (BAR) in California. They are the picky ones. And they work along with the California Air Resources Board (CARB).
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Mine used to do that until I got with Chris at Tillmans and we talked about it and was able to tune it almost completely out. It is annoying


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post #12 of 15 (permalink) Old 03-31-2010 Thread Starter
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Quote:
Originally Posted by travelers View Post
Mine used to do that until I got with Chris at Tillmans and we talked about it and was able to tune it almost completely out. It is annoying
awesome info. i will have to make a trip over to my performance shop to talk to my tuner sometime.

2005 Mustang GT
Paxton Novie 1200SL, Comp NSR Blower Grind 2, MMR Shortblock, C&L 95mm Mass/Air sensor, 39lb injectors, Motoblue ignition coils, Motoblue throttle plate spacer, Borla XR-1 Long Tube Headers and no cat x-pipe, Hooker Aero Chamber muffler, Custom LaMotta Performance tune, G-force tires, B&M shifter, Kennybell b-a-p, AEM analog A/F gauge, Interceptor scan gauge, McLeod RST clutch, aluminum flywheel
intercooler/smaller pully to come...
and yes it is my DD
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my guess, if its not the computer doing it based on wheel speed, its because the rear end is in motion but thats just a wild guess :smilie

One thing I've noticed that's different about my gt then my v6. When I shift into drive and I'm sitting on the brake the whole car roles forward just enough to feel it, like a jolt, then the brakes stop it and the car is basically pushing itself against the breaks. Very cool feeling.

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If the IAC (idle air control) is anything like the ones from the 96-04 4.6 Mustangs, one way to fix this is by installing a "restrictor plate" or a copper pipe cap with a 5/16" hole drilled into it to help bring the revs down.
IAC Restrictor Plates Slow Dropping/Hanging RPM fix - IMBOC
From what I've read, the IAC is calibrated to make the engine rev down slowly for emissions reasons. Doing this mod will fix that, and make it rev down like a carbureted car would. I've done this before on my 04. Not sure if it would work the same in the s197.

2007 Mustang GT/CS coupe
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There is no IAC on these cars. They are completely electronic throttle control now.


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