• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

Interesting Question

  • Thread starter Thread starter mkk50
  • Start date Start date Sep 17, 2005
M

mkk50

Active Member
Apr 5, 2005
109
29
39
Sep 17, 2005
#1
  • Sep 17, 2005
  • #1
Ok, i have been messing around with a high idle, and so far have gotten no where. Right now, the IAC is unplugged, and the car idles at 800 and is very smooth when warm. When cold, it idles around 900 and hunts a little. That 800 is with the throttle plate closed completly. All the air that is getting past is through that little hole. I have cleaned the MAF, EGR, Throttle body and tested the vac, coming up with 19 psi. Any1 have any tips to why my car idles soooo damn high?
 

DMAN302

My mom says thanks for the pearl necklace.
Nov 8, 2003
2,120
2
59
windsor, Canada
Sep 17, 2005
#2
  • Sep 17, 2005
  • #2
for me anything under 850 and I've got a miserable little girl on my hands. Likely your going to have to accept a few quirks with a HCI car unless your willing to pay to have a chip bunt. My idle will hunt aprox 100 RPM between 850-900 and it runs exceptionally well when dialed in therel.
 
M

mkk50

Active Member
Apr 5, 2005
109
29
39
Sep 17, 2005
#3
  • Sep 17, 2005
  • #3
i think u read planned mods, not mods i have already done
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
Sep 17, 2005
#4
  • Sep 17, 2005
  • #4
Do you have a hole in the butterfly (was that the reference to the little hole)?
 
M

mkk50

Active Member
Apr 5, 2005
109
29
39
Sep 17, 2005
#5
  • Sep 17, 2005
  • #5
yea there is a small hole in the butterfly
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
Sep 17, 2005
#6
  • Sep 17, 2005
  • #6
That hole will do it. Some have blocked it off to lower the idle (I wouldnt - you dont want something to dislodge in the TB).

You could probably do a real temporary (dont drive the car) blocking of the hole and note if the idle comes down.

Good luck.
 

DMAN302

My mom says thanks for the pearl necklace.
Nov 8, 2003
2,120
2
59
windsor, Canada
Sep 17, 2005
#7
  • Sep 17, 2005
  • #7
yikes..sorry. In that case I'd spend some serious time checking for vac leak..good readings on the gauge can be misleading..the small vac lines running throughout the bay become quite brittle with age and can break and crack very easily reaking havoc on idle.
 
M

mkk50

Active Member
Apr 5, 2005
109
29
39
Sep 17, 2005
#8
  • Sep 17, 2005
  • #8
i did block off the hole with a small screw at one point, and the car wouldn't idle. I would start it, and it would die almost instantly, even with the IAC connected
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
Sep 18, 2005
#9
  • Sep 18, 2005
  • #9
mkk50 said:
i did block off the hole with a small screw at one point, and the car wouldn't idle. I would start it, and it would die almost instantly, even with the IAC connected
Click to expand...
You are a tough guy to make happy. First it idles too high, then not high enough...... J/K man.

Since you have too much idle with the hole, you would have to block the hole and then play with the mechanical idle adjustment. Then see how it does. A bypass plate might even be needed so you can choose how much air-bleed is allowed.

No great ideas from me. Good luck.
 

olymaster

New Member
May 15, 2005
179
1
0
columbus ga
Sep 18, 2005
#10
  • Sep 18, 2005
  • #10
my car with mods running stock comp tried to idle at 600 or so and would studder and fall
after dyno and tune tunner set mea t 850 and its perfect
 

jrichker

StangNet's favorite TOOL
In Remembrance. Thank you for your contributions
Mar 10, 2000
27,512
2,811
234
Dublin GA
Sep 18, 2005
#11
  • Sep 18, 2005
  • #11
DMAN302 said:
yikes..sorry. In that case I'd spend some serious time checking for vac leak..good readings on the gauge can be misleading..the small vac lines running throughout the bay become quite brittle with age and can break and crack very easily reaking havoc on idle.
Click to expand...
Excellent advice - give it a try...
 

just4bob50

Active Member
Apr 2, 2005
504
5
28
Pa.
Sep 18, 2005
#12
  • Sep 18, 2005
  • #12
when my starts up cold it idles at about 1100 for 30secs to 1 min. then drops to 800rpms. and stays there. most guys i know with more than a couple bolt ons end up idling around 800 any how. Hell just doing the 10 min. tune up makes the car idle higher if you dont go back and reset the mech idle and tps. But thats alot of hassle to just drop idle 150 rpms if you ask me.
 
M

mkk50

Active Member
Apr 5, 2005
109
29
39
Sep 18, 2005
#13
  • Sep 18, 2005
  • #13
well i got mine idling around 700 to 800 now, w/o the iac connected. It runs like ass on first start, but as soon as it warms up, its smooth as silk. Plus the rpms drop so fast when shifting i almost can't keep up. I think i'll keep it like this.
 
M

mkk50

Active Member
Apr 5, 2005
109
29
39
Sep 18, 2005
#14
  • Sep 18, 2005
  • #14
got another small question now. By the ECC test module, there is a pack of wires that goes into the wiper motor. Two of the three plugs that come of that pack go into the motor, however there is one other connector, that has 2 plugs, that just hangs there. Does any1 know where that little connector goes?
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
Sep 18, 2005
#15
  • Sep 18, 2005
  • #15
The EEC self test port is in that neighborhood......
 
M

mkk50

Active Member
Apr 5, 2005
109
29
39
Sep 18, 2005
#16
  • Sep 18, 2005
  • #16
yea that plug is there too, but thats only 1 wire. This is different then that
 
You must log in or register to reply here.

Similar threads

7
Engine Random hanging idle
  • 706 Saleen
  • Feb 11, 2026
  • Fox 5.0 Mustang Tech
Replies
9
Views
435
Fox 5.0 Mustang Tech Feb 19, 2026
86HO5.0
8
S
Fuel ‘88 GT Runs Rich Cold — Fixes Itself When I Unplug Sensors (ECT, MAF, O2, etc.)
  • Sufarry
  • Nov 6, 2025
  • Fox 5.0 Mustang Tech
Replies
12
Views
720
Fox 5.0 Mustang Tech Nov 9, 2025
Mustang5L5
Engine Surging idle on start-up
  • keel
  • Aug 11, 2025
  • Fox 5.0 Mustang Tech
Replies
16
Views
765
Fox 5.0 Mustang Tech Oct 31, 2025
keel
C
Engine Code 13 and high idle
  • CmdrDerp
  • Dec 14, 2024
  • Fox 5.0 Mustang Tech
Replies
17
Views
800
Fox 5.0 Mustang Tech Dec 21, 2024
manicmechanic007
8
Engine Rough idle and aggressive sputtering when accelerating
  • 88vertible
  • Aug 13, 2025
  • Fox 5.0 Mustang Tech
Replies
4
Views
1K
Fox 5.0 Mustang Tech Dec 13, 2025
Jarhead67
J
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?