Irregular idle on Deceleration - Page 10 - MustangForums.com



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Old 04-15-2013, 12:35 AM   #91
JCON
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Did this issue ever get solved? My 2005 GT has 52,000 miles on it and since last summer I have had sporadic idle problems. When I installed my ram air intake and would coast in neutral to a stop, it would nearly stall (multiple times a day). After running the intake for a few weeks I switched back to stock (and have been there since) and still have the issue although not as often or as dramatic. Usually now I get a stuck throttle at 1000 rpms sitting at a light or dipping to 4-500 when going from reverse to clutch in to go to 1st. I thought initially it might be my TB or TPS, so I got another one. Problem remained. I just bought another take off TB with TPS and the issue seemed to be solved for a few weeks and then about two weeks ago it started to come back. I have not checked the vacuum lines yet but here's where I am:

2005 Mustang GT 5-speed
52,000 miles
Multiple TB, MAF, and idle air tube cleanings
Battery has been replaced
Full off road exhaust with a tune to turn off rear O2's
Stock air box
Fuel filter at 40,000
HT Autolite plugs checked and re-gapped summer 2012

I do not remember the problem before the ram air intake install which was a month after the long tube install. The tune I am running now is not the stock tune. With the ram air intake installed, I did have the car fail safe a few times after WOT runs. I wonder if the dashpot tables are incorrect in the tunes since I have run the 91 octane ram air intake tune, 91 stock intake tune, and 87 stock intake tune (all by the same tuner but not custom for my car, just using known values) all with the same dropping idle problem while decelerating.

Anyone get a fix for this? I am planning to add delete plates, under drive pulleys, and the intake again and getting an actual dyno tune to see if this clears it up (but not before summer).
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Old 04-15-2013, 04:19 AM   #92
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Can the charge motion plates in the stock intake manifold cause this problem without throwing a code? I'm not entirely sure how they work, since mine have been removed for most of my cars life, but they are basically another throttle body.
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Old 04-15-2013, 06:25 AM   #93
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Subscribed! I get this problem with my 2010 GT. got the problem with Bama tunes and now with Steeda Tunes and they both told me "there is nothing wrong with the tune." Took it to the dealer and they said "there is nothing wrong with the car". Obviously, someone is incorrect.
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Old 04-15-2013, 07:23 AM   #94
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moose, I suppose it is possible that the plates are causing a problem but I think it is unlikely. I don't know much about how smooth the transition from open to closed (even though at closed they are ~45% open) is to know if the sudden closing causes stalling. Was hoping the ops before would post a solution. I'll keep this up to date. Seems to be a 4.6L issue.
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Old 04-15-2013, 08:45 AM   #95
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I had kind of the same problems when I installed my cams - hanging rpms, dipping rpms on decel and at idle, stalling, etc. Wasn't the throttle body (it isn't stock anyway). It was a tune problem - dashpot settings needed to be tweaked for more idle fuel and throttle closing rate.
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Old 04-15-2013, 11:03 AM   #96
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Quote:
Originally Posted by jpplaw View Post
I had kind of the same problems when I installed my cams - hanging rpms, dipping rpms on decel and at idle, stalling, etc. Wasn't the throttle body (it isn't stock anyway). It was a tune problem - dashpot settings needed to be tweaked for more idle fuel and throttle closing rate.
My question is this: How can I convince a tuner to look into the settings, if they swear up and down there is nothing wrong with the tune? I've asked Steeda to look into the dashpot settings, and have been told "there is nothing to adjust, the tune is fine."
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Old 04-15-2013, 11:23 AM   #97
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Find a new tuner... try Tillman Speed or BrenSpeed
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Old 04-15-2013, 11:30 AM   #98
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Call Brenspeed and talk to Brent and explain what the car is doing. I am sure he can fix you right up
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Old 04-15-2013, 04:43 PM   #99
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brenspeed fixed my hanging rpms with the frpp throttle body. They didn't actual hang so much as they just took much longer to come down than the stock throttle body.
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