2003 Mustang V6 Very High Idle Help! - Ford Mustang Forum
 
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post #1 of 9 (permalink) Old 11-25-2010 Thread Starter
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2003 Mustang V6 Very High Idle Help!

I installed a Windstar Intake from VAP Auto back in June and ever since Ive had a couple problems. The first was a cruise control issue that I have since resolved, the second is an unusually high idle. When starting my car, and as long as its in P or N, the idle likes to either surge up to 2,000RPM and even 2,500RPM and stays there, or it creeps up to 2,000/2,200RPM and just hangs. It doesnt do this ALL the time, so Im confused... Also, after Seafoaming my intake through the brake booster, it was nearly gone for a couple weeks, occurring only twice during that time. My current mods are below:

Windstar Intake
65mm GT TB
Spectre CAI filter element
Monza/Pacesetter LT Headers
Monza X-Pipe
Magnaflow cats
Borla Catback on CME tips

Thats pretty much it... Looking for others' opinions... I have no clue on what the problem could be, there is no CEL or SES light, no trouble codes, nothing an OBDII scanner is picking up... Any help would be appreciated!

Edit: Also, the car is very pushy. While shifting, while just letting it crawl, etc. For example, while in D, the idle is around 1,000RPM. Shift out of D into R and the car skips and spins a bit cause the idle goes up to 1,500RPM before going into R gear...

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post #2 of 9 (permalink) Old 11-25-2010
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I would try replacing the idle air control valve. i had the same type of thing happen on my gt stang. If not try adjusting the idle control screw, should be by the throttle body. When adjust your idle screw, unplug your idle air control valve. If its adjusted right it should almost stall out, or idle very low, like 500 rpms. if its still idling high, adjust the idle screw till your car almost dies when the idle control valve is unplugged and when you plug in your idle air control valve it should bring the rpms up again to normal, hope this help you out.
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post #3 of 9 (permalink) Old 11-25-2010
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i sort of wonder if your throttle or cruise cable is holding it open a little

2003 3.8L V6 4R70W
Windstar Upper Intake with cool-air intake, MAC LT headers, BBK O/R H-pipe, and flow 40s, SCT tuner, FRPP Alum. D/S, 3.73 gears, Auburn HP limited slip, and Team Z LCAs, Eibach sway bars.
Best 1/4 time: 15.036 @90.92mph, 2.148 60'
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post #4 of 9 (permalink) Old 11-26-2010
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Whats the GT throttle body about? Did you use a 4.6L GT TB or what?

Jesse Berger
90 LX, Previous 4 cyl.
408W In the Works
TW FAC's, Jay Allen cam, Super Victor

2001 V6 5 Speed Daily Driver
Windstar Intake, Dual Exhuast, CAI, Headers
Best ET: 15.44@91 mph (on 18's)
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post #5 of 9 (permalink) Old 11-26-2010 Thread Starter
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Quote:
Originally Posted by 02yellowstanggt View Post
I would try replacing the idle air control valve. i had the same type of thing happen on my gt stang. If not try adjusting the idle control screw, should be by the throttle body. When adjust your idle screw, unplug your idle air control valve. If its adjusted right it should almost stall out, or idle very low, like 500 rpms. if its still idling high, adjust the idle screw till your car almost dies when the idle control valve is unplugged and when you plug in your idle air control valve it should bring the rpms up again to normal, hope this help you out.
I will try that on my next day off..

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Originally Posted by Markstang690 View Post
i sort of wonder if your throttle or cruise cable is holding it open a little
Can't be, it will high rev even when the TB cable is disconnected... There's so much slack in the cable I rooted that out firsthand...

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Originally Posted by StalkerStang View Post
Whats the GT throttle body about? Did you use a 4.6L GT TB or what?
It's a new VAP thing, instead of a 60mm TB, I paid an extra $40 for a larger 65mm GT TB... I will take pictures and post it on this thread so everyone can see my setup

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post #6 of 9 (permalink) Old 11-26-2010 Thread Starter
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Here is a pic, the only one I have on my iPhone right now, will take a few with mr camera tomorrow... Btw, I'm sorry if I take a while to respond, I work 3 jobs... Wanna pay off the Stang already

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post #7 of 9 (permalink) Old 11-27-2010 Thread Starter
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Trying photo uploader again...
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post #8 of 9 (permalink) Old 11-30-2010
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For a high idle symptom, the most likely cause is excessive air after the throttle body. This could be from a vacuum leak or from the idle set screw being set too high (already mentioned).

Remember that the IAC is a bypass device. As such, the IAC requires that the TB butterfly block almost ALL air when the throttle is CLOSED. Then and only then can the IAC control the idle by bypassing air around the TB butterfly.

The IAC can only ADD bypass air. Never subtract.

Sooooo. if the TB idle set screw is allowing too much air to pass, the IAC can NOT slow the idle because there is no adjustment left.

As mentioned already, disconnecting the IAC electrical connector must result in a decrease in RPM's. The idle should be very slow or the motor die outright with the IAC disconnected.

Also, if there is a vacuum leak allowing unmetered air to enter the intake, the driveability will never be correct.

Please review the following post for more information on how the IAC works.

http://www.allfordmustangs.com/forum...ml#post2260649

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2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.
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post #9 of 9 (permalink) Old 12-24-2010 Thread Starter
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Quote:
Originally Posted by wmburns View Post
For a high idle symptom, the most likely cause is excessive air after the throttle body. This could be from a vacuum leak or from the idle set screw being set too high (already mentioned).

Remember that the IAC is a bypass device. As such, the IAC requires that the TB butterfly block almost ALL air when the throttle is CLOSED. Then and only then can the IAC control the idle by bypassing air around the TB butterfly.

The IAC can only ADD bypass air. Never subtract.

Sooooo. if the TB idle set screw is allowing too much air to pass, the IAC can NOT slow the idle because there is no adjustment left.

As mentioned already, disconnecting the IAC electrical connector must result in a decrease in RPM's. The idle should be very slow or the motor die outright with the IAC disconnected.

Also, if there is a vacuum leak allowing unmetered air to enter the intake, the driveability will never be correct.

Please review the following post for more information on how the IAC works.

http://www.allfordmustangs.com/forum...ml#post2260649

Sorry for the late reply! I had some other issues with the car to deal with, not to mention break time being limited by the holiday season and lots of garage cleaning... T.T

Now that I finally have a break, I will check this tomorrow or the following day... I disconnected my battery yesterday and the car runs fine now, but like always I know it will start to high idle again sooner or later... Thanks for the info, I will first try unplugging the IAC connector to see if the RPMs change or motor dies.

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