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Irregular idle on Deceleration

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Old 08-14-2010, 07:40 AM   #61
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Old 10-02-2010, 04:46 PM   #62
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Any updates ?
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Old 11-28-2010, 03:18 PM   #63
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Originally Posted by cfr865 View Post
Any updates ?


Still having problems with it after brenspeed sent me a new tune.


I am really at a loss until something on the car breaks or it throws a engine code. I did recently read something about idle problems possibly having to do with the ac compressor but nothing confirmed.
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Old 11-29-2010, 10:43 AM   #64
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Quote:
Originally Posted by dkersten View Post
Just an FYI update.. I fixed my problem with idle and surging by putting an air dam around the intake filter.. My filter was exposed, however, and the air blowing directly on it was causing turbulence in the MAF housing, which was causing the problems..
I am also very interested in this. I have had similar problems for almost 2 yrs but have the SC and Cams so figured it was just part of it. I had it on my other Foose stang also which just had the hot rod cams and no blower, but did have an aftermarket CAI.

I would really like to see some pictures or a better description of what you did to create an air dam. I might want to try the same. My air filter is pointed towards the front fender and open on the end and on the top side because I do not have an underhood insulating blanket. Was removed because of chaffing and I show the car. My setup...
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Old 11-29-2010, 07:02 PM   #65
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I am also very interested in this. I have had similar problems for almost 2 yrs but have the SC and Cams so figured it was just part of it. I had it on my other Foose stang also which just had the hot rod cams and no blower, but did have an aftermarket CAI.

I would really like to see some pictures or a better description of what you did to create an air dam. I might want to try the same. My air filter is pointed towards the front fender and open on the end and on the top side because I do not have an underhood insulating blanket. Was removed because of chaffing and I show the car. My setup...


My hood doesnt have any insulation under it. And I honestly still havent took the time to make any pieces out of sheet metal to block off my ram air holes. Why? because the hood was on for over a year without any problems so I highly doubt that will do anything but waste my time especially because the rpm jumps at a stand still without any movement.

I just dont get how so many people are having this problem yet no one has figured out a fix yet. I have spent hours on the phone with brenspeed, hours at a local performance shop, hours at a ford dealership and hours on the net researching and I still have no clue and it doesnt seem like anyone else does either.
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Old 11-29-2010, 10:34 PM   #66
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I have had a smiliar issue, I also have the acceleration hesitation after long cruise issue, I suspect my fuel pump, it is still original, I want to get it replaced under TSB but dont want to leave it at dealer and have them rack up tons of highway miles to recreate problem, but that issue coupled with irregular idle RPM and sputtering on decel for me points to possibly crappy fuel pump ! what do you think ?
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Old 11-30-2010, 11:14 AM   #67
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Originally Posted by desslok40 View Post
I have had a smiliar issue, I also have the acceleration hesitation after long cruise issue, I suspect my fuel pump, it is still original, I want to get it replaced under TSB but dont want to leave it at dealer and have them rack up tons of highway miles to recreate problem, but that issue coupled with irregular idle RPM and sputtering on decel for me points to possibly crappy fuel pump ! what do you think ?
FWIW, I made a copy of that TSB, and gave it to my dealer. They replaced the fuel pump with no questions asked, and no extensive road testing.

An erratic idle rpm can be caused by a dirty throttle body. Auto parts stores sell aerosol products designed specifically to clean it.
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Old 11-30-2010, 11:58 AM   #68
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Originally Posted by desslok40 View Post
I have had a smiliar issue, I also have the acceleration hesitation after long cruise issue, I suspect my fuel pump, it is still original, I want to get it replaced under TSB but dont want to leave it at dealer and have them rack up tons of highway miles to recreate problem, but that issue coupled with irregular idle RPM and sputtering on decel for me points to possibly crappy fuel pump ! what do you think ?

I have actually thought this could be the problem as well but since my car isnt under factory warranty anymore only power train its one of those things where I am waiting for it to go if it is the problem. I cant say I have heard much about a fuel pump causing the rpm to bounce in these mustangs though.



Quote:
Originally Posted by ski View Post

An erratic idle rpm can be caused by a dirty throttle body. Auto parts stores sell aerosol products designed specifically to clean it.


Everyone knows to clean their TB especially in this thread. Its like a parrot flys into the room every time someone says bad idle to repeat "oh its your tb"... or not.
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Old 11-30-2010, 03:02 PM   #69
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Quote:
Originally Posted by simplexdesign View Post
I have actually thought this could be the problem as well but since my car isnt under factory warranty anymore only power train its one of those things where I am waiting for it to go if it is the problem. I cant say I have heard much about a fuel pump causing the rpm to bounce in these mustangs though.
I can almost guarantee this is not a fuel pump issue. I changed out my factory pump to the dual GT 500 Pumps when I went SC and it had no effect. My other Foose had the same issue but was stock pump and hot rod cams. Car only had about 1000 miles on it when I had the cams installed and noticed the problem shortly after.
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Old 11-30-2010, 09:30 PM   #70
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Quote:
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I can almost guarantee this is not a fuel pump issue. I changed out my factory pump to the dual GT 500 Pumps when I went SC and it had no effect. My other Foose had the same issue but was stock pump and hot rod cams. Car only had about 1000 miles on it when I had the cams installed and noticed the problem shortly after.



I dont know if that is good news or bad news because at this point I want it to be something.... I am gonna go hug my car and cry now lol
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Old 11-30-2010, 09:44 PM   #71
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did you ever raise your idle rpms? if not, you might try setting
drive idle rpms to 1000 and nuetral idle rpms also to 1000. it
might make the car less annoying, while you troubleshoot for
the real issue.
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Old 12-01-2010, 10:28 AM   #72
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Quote:
Originally Posted by hammeron View Post
did you ever raise your idle rpms? if not, you might try setting
drive idle rpms to 1000 and nuetral idle rpms also to 1000. it
might make the car less annoying, while you troubleshoot for
the real issue.


I doubt bumping the idle up would help because most of the time its too high already. Plus I dont want to try to patch the issue I would rather it get worse until the problem becomes more obvious.
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Old 12-01-2010, 10:47 AM   #73
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yeah i understand.

well ham is on the job now, so we'll get this bugger fixed come he11
or high water.
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Old 12-01-2010, 11:27 AM   #74
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So here is my thoughts Ham.

If the fuel trims are okay, which seem like they probably are since the OP has not talked about a lean or rich condition in the CELs, then I would have to guess it may be in the dashpot. The dashpot controls either throttle plate or fuel/air input per gear. I recall when I my car was getting tuned earlier this year I had a surging while decelerating in gear and an hunting idle.

The tuner changed the values within the dashpot and the issue is almost completly gone. 2nd and 3rd gear could use some slight adjustment but it's okay.

I doubt it's a MAF issue since they seem to just completly die instead of work intermitantly.

O2 sesnor would throw those codes per bank, most likely.

The strange thing is with a stock tune and intake it does it? Is there a ghost in the software?
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Old 12-01-2010, 11:51 AM   #75
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i like your thoughts on the subject simon1. the stock tune with stock airbox, coupled
with surging rpms while the car is sitting still...is very interesting.

i've got to go back over this thread and outline what has and hasn't been tried, then
try to lay out a troubleshooting sequence.
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Old 12-01-2010, 03:39 PM   #76
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Hammeron... been a while dude. Hope you have been doing good.

Anyway, in reading through all of this, it reminded me of something strange that happened to me last winter which might help in the overall thought process. As stated, I have had this problem for a very long time and just learned how to deal with it. However, back over last winter, I had my battery die. When I replaced it and even reflashed the tune, there was something wrong with the tune. I even flashed multiple times. But the result was that my idle for both neutral and in gear were at about 1000 - 1100 and I had no idle surging or hunting issues. It was as if the aftermarket tune was not registering. My speedometer was also off and the tune was not recognizing the change in tire size. After about a month of riding around like that I disconnected the battery, uploaded the stock tune and then the aftermarket tune and everything was back to as it should be... including the idle surge and hunting issue! Just food for thought in this analysis.
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Old 12-01-2010, 06:40 PM   #77
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Quote:
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Hammeron... been a while dude. Hope you have been doing good.
it has been awhile, doing good and good to see you visiting the board again.

i like these kinds of problems because they force us to learn about the way things
ought to be, in order to figure out what is going wrong. in this case, we need to learn how the pcm controls idle in a normally operating vehicle. for me, that's the next step.
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Old 12-02-2010, 12:41 PM   #78
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here's a review of simplex's comments over the last 10 months, so we can see
what's been done to date:



02-01-2010
It usually happens when I am slowing down and I put the car in neutral the rpms
will go down and then start jumping around under and over 1k without applying
the gas pedal at all.



02-05-2010
Cleaned my MAF sensor(Wasnt very dirty), took out battery, re-installed tune and
I am still having the problem.



03-23-1010
At this point I have Cleaned the MAF Sensor, Cleaned the Throttle Body, Changed
the Spark Plugs, Changed the Fuel Filter, Took out Battery and Re-Installed my
Brenspeed 93 tune



03-24-2010
Cleaned Air Filter, All bolts are tight, The Throttle body got completely taken
off and cleaned.



04-20-2010
They came back with a low voltage on the TB so they recommended to replace it.
Obviously I wasnt going to pay their $500+ to install one so I ordered a new take
off TB from Brenspeed installed it and I am still having the problem.



04-20-2010
The few Vacuum lines have been checked.



05-28-2010
I went to ford earlier this week and had them reflash the pcm and I reinstalled
my factory airbox and sure enough it seems like the problem is gone.



06-19-2010
As of right now I have only driven the car maybe 100 miles and I honestly think
that ford reflashing the pcm masked the problem and the computer is just
correcting/adapting to it.



07-17-2010
Problem is back and it is factory tuned with factory airbox back on so I am really
lost to what the problem is.



11-29-2010
the rpm jumps at a stand still without any movement.






MODS: The only real motor mod is a tune and intake by brenspeed running a 91 octane
tune with exhaust work.
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Old 12-02-2010, 01:33 PM   #79
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Damn hammeron thanks for laying that all out like you did I appreciate the attention to the thread. I just realized this problem is coming up on a year of existing which is entirely to long.
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Old 12-02-2010, 02:12 PM   #80
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you are welcome and we're all happy to help get this sorted out. i think
simon1 is on the right track with thinking about dashpot function. i've started
looking at the service manual for clues and also my advantage III help files, which
explain quite well how idle is managed. i just have to let it sink in for awhile
before i can make heads or tails of it.
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Old 12-02-2010, 02:12 PM
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