Stalling on deceleration?

M

MYSTICSVT

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May 16, 2001

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Meridian, Idaho

Aug 1, 2006

#1

• Aug 1, 2006

• #1

My Mustang starting stalling yesterday at stoplights. It only does it in drive and when it's warm. Thankfully it refires right back up and idles. If I shift into neutral before I stop it stays running. The car seems to run fine other than at idle. No problems with accelleration or cruise, just idle. Anyone have any suggestions where I should start looking?

 

T

TENGRAM

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#2

• Aug 1, 2006

• #2

most likely your IAC valve (on the frontside of the TB) needs to be cleaned or replaced. take it off and spray carb cleaner in it. let it dry out and reinstall.
the vehicle speed sensor is also utilized in the "strategy" for preventing stalling on deceleration.

 

HISSIN50

"How long does it take to get help in here?

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#3

• Aug 1, 2006

• #3

If you set the idle with the IAC connected and being used (having a duty cycle), the IAC might be dirty.

I choose to set the idle with the car in drive and the IAC disconnected (and no load on the engine).

Good luck.

 

M

MYSTICSVT

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May 16, 2001

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Meridian, Idaho

Aug 1, 2006

#4

• Aug 1, 2006

• #4

TENGRAM said:

most likely your IAC valve (on the frontside of the TB) needs to be cleaned or replaced. take it off and spray carb cleaner in it. let it dry out and reinstall.

Click to expand...

Thank's, I'll try that first.

 

vristang

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#5

• Aug 1, 2006

• #5

Vehicle Speed Sensor?

 

larrendeuce

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Sep 13, 2003

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Southern NJ

Aug 1, 2006

#6

• Aug 1, 2006

• #6

Mine did that when I didn't have in a speedo gear, only stalled when I used the air conditioning though.

 

M

MYSTICSVT

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May 16, 2001

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Meridian, Idaho

Aug 2, 2006

#7

• Aug 2, 2006

• #7

Cleaned out the IAC this morning. Didn't look like it needed it though. It was spotless inside. The car now has a slightly rough idle and is picking up an off idle stumble. Any ideas? TFI module maybe? The car only has 75K miles and it looks like the original one. Anyone?

 

D

DeVus1

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P-Town, Va.

Aug 2, 2006

#8

• Aug 2, 2006

• #8

Clean out the mass air meter as well. Then disconnect the battery and let the computer reset its memory.

 

M

MYSTICSVT

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Meridian, Idaho

Aug 2, 2006

#9

• Aug 2, 2006

• #9

DeVus1 said:

Clean out the mass air meter as well.

Click to expand...

With what? Carb clean?

 

HISSIN50

"How long does it take to get help in here?

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#10

• Aug 2, 2006

• #10

At that point, I'd pulll codes and check for vac leaks.

Good luck.

 

gcwh02

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Jun 20, 2005

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Aug 2, 2006

#11

• Aug 2, 2006

• #11

suscribing, I have same problem

 

vristang

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#12

• Aug 2, 2006

• #12

Carb cleaner should work.
I always use brake cleaner, for the lack of residue.

Some folks use a Q-tip, but I have found it not to be necessary when using brake cleaner.

 

gcwh02

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pottstown, PA

Aug 2, 2006

#13

• Aug 2, 2006

• #13

HISSIN50 said:

If you set the idle with the IAC connected and being used (having a duty cycle), the IAC might be dirty.

I choose to set the idle with the car in drive and the IAC disconnected (and no load on the engine).

Good luck.

Click to expand...

By IAC disconnected do you mean just disconnecting the electronics to it? or the whole thing? I had my TPS adjusted while the IAC was connected, could that be a problem?

 

HISSIN50

"How long does it take to get help in here?

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#14

• Aug 2, 2006

• #14

gcwh02 said:

By IAC disconnected do you mean just disconnecting the electronics to it? or the whole thing? I had my TPS adjusted while the IAC was connected, could that be a problem?

Click to expand...

You got it - disconnect the IAC electrical connector.

When you do this, you are assuming a baseline IAC duty cycle of 0%. You set your idle where you want it (on a hot motor with no electrical load like AC or lights, etc). Then clear the KAM (disconnect the battery, turn on headlights for 30 seconds, turn headlights off and reconnect battery). What you have done is set the idle at or above the factory setting without IAC input. This means the computer cant try to lower your setting, and it knows what the stock setting is and will try to get the idle lower. The only way it can feasibly do this is to shut the IAC, which you did when you set the idle. Cool!

Logic: When people set the idle with the IAC connected, it leaves room for the computer to remove IAC duty cycle (because there was some while setting the idle). This can lead to a hunting idle and surging.


Now on the TPS: it related to the computer the amount of throttle blade openness (word?). The IAC changes the idle without moving your throttle blade (as opposed to the idle stop screw, which DOES change the throttle blade position).

So cleaning the IAC should not affect the TPS setting. But when you change the idle setting with your idle stop screw, you can check the TPS reading to make sure it's still copacetic.

Good luck.

 

gcwh02

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Jun 20, 2005

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Aug 2, 2006

#15

• Aug 2, 2006

• #15

its getting worked on tomorrow so I'll let you guys know what I come up with... never ending problems

 

M

MYSTICSVT

Founding Member

May 16, 2001

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Meridian, Idaho

Aug 3, 2006

#16

• Aug 3, 2006

• #16

Thank's for all the help guys. I checked for codes and found a 29 and a 66. So I cleaned the MAF, replaced the VSS, and cleared the codes. All is perfect now. No more rough idle or stalling. And as an added bonus, my cruise had been working intermittantly, and now it's working constantly. :SNSign:

 

D

DeVus1

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P-Town, Va.

Aug 3, 2006

#17

• Aug 3, 2006

• #17

MYSTICSVT said:

Thank's for all the help guys. I checked for codes and found a 29 and a 66. So I cleaned the MAF, replaced the VSS, and cleared the codes. All is perfect now. No more rough idle or stalling. And as an added bonus, my cruise had been working intermittantly, and now it's working constantly. :SNSign:

Click to expand...

Good news.

 

M

MYSTICSVT

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May 16, 2001

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Meridian, Idaho

Aug 5, 2006

#18

• Aug 5, 2006

• #18

Well guys, it looks like I spoke too soon. My rough idle has returned. It starts idling fine and then just gradually gets worse until it stalls. Only does it in Drive. In Park it idles a little rough, but doesn't stall. I checked for codes again, but there are none on KOEO or KOER. Anyone have a suggestion? Since it disappeared for a little while after I cleaned the MAF is it probably the MAF going south?

 

jrichker

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Aug 5, 2006

#19

• Aug 5, 2006

• #19

See "Help me create the Surging Idle Checklist" at http://forums.stangnet.com/showthread.php?t=534062
for help with your idle problems. The first post contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.