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

Startup issue

  • Thread starter Thread starter Mstng93SSP
  • Start date Start date Apr 25, 2019

Mstng93SSP

You have a nice rear end there Dave.
15 Year Member
Nov 29, 1999
2,993
3,500
184
Mililani, Hawaii
Apr 25, 2019
#1
  • Apr 25, 2019
  • #1
I am having an irritating issue. Lets say an initial startup on a fox goes something like this. Fires up, rpm goes to around 1100, then slowly drops to 1000, the slowly settles down to idle rpm of 850ish (or whatever your normal idle is) and then idles normal. What mine does is this. Fires up, rpm goes to around 1400 for 1 to 3 seconds, then quickly drops to 1100, and then slowly to 1000, and then slowly drops to idle as it should normally. So, everything on my startup is normal except for that initial 1400 rpm for 1 to 3 seconds before dropping to the normal idle sequence. I scanned and got no codes to indicate a problem. Other than this the car runs and drives fine. I have had two different ECU's in the car, it did the same with both.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
27,826
10,507
203
polk county florida
Apr 25, 2019
#2
  • Apr 25, 2019
  • #2
Ever clean you egr or your air idle control valve?
 

jrichker

StangNet's favorite TOOL
In Remembrance. Thank you for your contributions
Mar 10, 2000
27,512
2,811
234
Dublin GA
Apr 25, 2019
#3
  • Apr 25, 2019
  • #3
You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money.

Look for the base idle reset procedure to fix your problem. Unless you have a wild cam, the idle should be in the 650-725 range on a warm engine. Look for small vacuum leaks in the plastic hard lines that connect things to manifold vacuum.
 

Mstng93SSP

You have a nice rear end there Dave.
15 Year Member
Nov 29, 1999
2,993
3,500
184
Mililani, Hawaii
Apr 25, 2019
#4
  • Apr 25, 2019
  • #4
I have tried cleaning the egr and iap. I have spares, maybe I will try one.
 

BlakeusMaximus

Still got to try a little lube on my speedo head
5 Year Member
Jul 12, 2017
2,474
1,348
173
Apr 25, 2019
#5
  • Apr 25, 2019
  • #5
I think my car does that too SSP. Only when it’s a cold start though.
 

BlakeusMaximus

Still got to try a little lube on my speedo head
5 Year Member
Jul 12, 2017
2,474
1,348
173
Apr 25, 2019
#6
  • Apr 25, 2019
  • #6
I’m going to pull my intake off and redo it when I get it back home and I’ll probably replace all those lines.
 

Mstng93SSP

You have a nice rear end there Dave.
15 Year Member
Nov 29, 1999
2,993
3,500
184
Mililani, Hawaii
Apr 25, 2019
#7
  • Apr 25, 2019
  • #7
Yep. Cold only.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
27,826
10,507
203
polk county florida
Apr 26, 2019
#8
  • Apr 26, 2019
  • #8
I have a hard time starting when it's cold! And I stutter till after my first cup of coffee
 
You must log in or register to reply here.

Similar threads

Engine Surging idle on start-up
  • keel
  • Aug 11, 2025
  • Fox 5.0 Mustang Tech
Replies
16
Views
752
Fox 5.0 Mustang Tech Oct 31, 2025
keel
M
01 mustang 3.8 fuel pressure issue
  • Mhaley2006
  • May 29, 2026
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
0
Views
41
1996 - 2004 SN95 Mustang -General/Talk- May 29, 2026
Mhaley2006
M
K
Engine 2000 Mustang GT - Fuel issue post-blown spark plug repair
  • kenster1092
  • Feb 26, 2026
  • SN95 4.6L Mustang Tech
Replies
4
Views
283
SN95 4.6L Mustang Tech Mar 10, 2026
kenster1092
K
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
M
Engine 1988 Foxbody - Overheating Summer
  • MDrisc
  • Oct 26, 2025
  • Fox 5.0 Mustang Tech
Replies
10
Views
476
Fox 5.0 Mustang Tech Nov 28, 2025
Mustang5L5
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?