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10-09-2005, 06:11 PM | #1 |
Registered Member
Join Date: Oct 2005
Posts: 1
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idle air control valve problems on a 91 5.0
I have a 91 5.0 mustang with a 5 speed. The motor is pretty much
stock execpt for roller rockers, headers, pulleys, the mass air meter, 65mm throttle body, and a cold air intake. The vehicle was running fine with this combination. In fact it was running quite well until I put a Trick Flow street intake on it about a month ago. What happens is that the vehicle idles good and runs very well, but when I start to come to a stop and lets say I'm running 2k rpm and I push the clutch in and take my foot off of the accelator it sometimes wants to shut off. The vehicle cranks up fine and runs normal, but its annoying to have it shutting off while I'm coming to a stop. One mechanic told me it was either a vacume leak or the IAC valve. I checked for vacume leaks and could not find any. I replaced the IAC valve with one from Advance Auto Parts, and it doesen't shut off as much as the stock unit, but every once in a while it will. Any help will be appreciated. I have to fix this problem. Thank You. |
10-10-2005, 07:39 AM | #2 |
Moderator
Join Date: Aug 2000
Location: Milan, OH
Posts: 2,699
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Re: idle air control valve problems on a 91 5.0
You've changed the airflow into and out of the engine. What is happening is that the idle dashpot isn't sufficient enough to keep the engine from stalling on de-clutch. A good tuner would be able to adjust the idle preposition, dashpot and isc neutral air to restore the driving quality. Word of warning, if you attempt to add idle air by adjusting the idle stop screw on the throttle body, you'll most likely end up with a flare on the shifts and a surging idle. A custom tune is really the way to solve the driveability issue.
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Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!" |
10-12-2005, 12:32 PM | #3 | |
Rearview Mirror Haze
Join Date: May 1999
Location: Huntsville, Alabama...a.k.a. "HuntsVegas"
Posts: 387
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Re: idle air control valve problems on a 91 5.0
Quote:
Thanks Brett! You inadvertantly got that question answered for me as well. I don't want to take over thread, but what is a dashpot/ idle preposition/ isc neutral air? Does someone have a link showing how to do this one? I got major surging after fixing my vacuum leaks and adding a 1" spacer... Sorry Brett- I fugured you might ask anyway.
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93 lx Notch 01 GT ...the epitome of Murphy's Law |
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10-12-2005, 09:06 PM | #4 |
Moderator
Join Date: Aug 2000
Location: Milan, OH
Posts: 2,699
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Re: idle air control valve problems on a 91 5.0
These are all parameters or tables found in the PCM. They have to be accessed & changed through a custom program (chip). We use the SCT Advantage (Superchips Custom Tuning) at our shop but a shop using Autologic, Diablosport/Chipmaster, or other custom tuning software can make the necessary tuning changes for you.
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Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!" |
10-19-2005, 12:15 PM | #5 |
Mizzou Tigers
Join Date: Apr 1999
Location: weston, MO United States
Posts: 1,455
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Re: idle air control valve problems on a 91 5.0
Jeff, thanks for the info. I don't have my Stang anymore, but I fought that problem for years with it. All the IAC changes, resetting computer, changes to throttle screw position, etc. never seemed to totally eliminate my problems. This is the first I've heard of the parameteres you mention. Good info to know for future reference. Thanks! ( I am already planning out my next Stang purchase for this spring...the Conturd has got to go )
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2006 Mustang GT 1990 LX GT-40 motor 262 horsepower, 307ft-lbs (sold but forever loved) 1998 Contour SVT Rice Haters Club Member #244 |
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