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

1989 Fox, 5.0 High Warm Idle

  • Thread starter Thread starter hamirick
  • Start date Start date Jun 28, 2017
H

hamirick

Active User
Jun 14, 2017
15
4
13
Jun 28, 2017
#1
  • Jun 28, 2017
  • #1
Hey Guys,

Hoping for some guidance here. You guys have been a huge help so far, so thank you!!!

Alright, so, I'm new to actually adjusting an engine. I've swapped parts, and done chassis/suspension/body for year, but actually "tuning & adjusting", etc, I'm new to.

Right now, my cold start idle is about 500 - 700rpms, feels perfect for me. But when the car warms up to 190 - 200 degrees, the idle jumps to 1500 - 2000, which is way too high. Is ther an adjustment for the warm idle that I've overlooked? I used the adjustment bolt on the throttle body to set the idle, am I missing another adjustment screw/bolt or is this an electrical problem, etc?

Please let me know!

Thanks!
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,249
17,930
224
Massachusetts
Jun 28, 2017
#2
  • Jun 28, 2017
  • #2
Perform "idle reset procedure" and then drive around a bit and run the engine codes
 

jrichker

StangNet's favorite TOOL
In Remembrance. Thank you for your contributions
Mar 10, 2000
27,512
2,813
234
Dublin GA
Jun 28, 2017
#3
  • Jun 28, 2017
  • #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. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
 

Real time recon

Mustang Master
Aug 21, 2016
469
205
83
...
Jun 29, 2017
#4
  • Jun 29, 2017
  • #4
Seems to me 500 to700 cold start RPMs is a little low.
 
You must log in or register to reply here.

Similar threads

S
Engine Stalls when downshifting/coasting
  • Scott_S
  • Nov 5, 2025
  • Fox 5.0 Mustang Tech
Replies
11
Views
692
Fox 5.0 Mustang Tech Nov 6, 2025
Mustang5L5
C
Electrical HELP! 1989 5.0 Stick, Voltage Bleed onto Ignition Trigger wire
  • ChickenDeluxe
  • May 14, 2026
  • Fox 5.0 Mustang Tech
Replies
7
Views
216
Fox 5.0 Mustang Tech May 24, 2026
ChickenDeluxe
C
C
Engine Code 13 and high idle
  • CmdrDerp
  • Dec 14, 2024
  • Fox 5.0 Mustang Tech
Replies
17
Views
884
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
A
Rough idle - cylinder 1 and 6 misfire HELP
  • austindavies935
  • Jul 24, 2025
  • SN95 4.6L Mustang Tech
Replies
12
Views
697
SN95 4.6L Mustang Tech Jul 24, 2025
gkomo
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?