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

Idle problem

  • Thread starter Thread starter miser143
  • Start date Start date Friday at 9:06 AM
M

miser143

New Member
Oct 2, 2024
17
1
3
New york
Friday at 9:06 AM
#1
  • Friday at 9:06 AM
  • #1
Does eny one know what can the problem be this is on cold start. 1991 mustang gt 5.0 .tps is on .98v . New module new spark plug new idle control valve. Coil is good. Timing is done engine cooling temperature sensor is new .
 

DadLife0724

Advanced Member
Mar 22, 2024
408
272
73
Cooperstown, PA
Friday at 9:55 AM
#2
  • Friday at 9:55 AM
  • #2
Base idle reset would probably do you some good. Tell us more about your Mustang. And.......
 
M

miser143

New Member
Oct 2, 2024
17
1
3
New york
Friday at 10:37 AM
#3
  • Friday at 10:37 AM
  • #3
Also I smoked test it did not see nothing checked fuel pressure was at close to 40 psi .I disconnected the egr from the throttle body but still connected. But i but a plate on the thrutle. I have no ac .no smog pump connection. Maybe I have to replace the 02 sensor I have no cats all straight pipe. Underload it turn off sometimes.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
28,065
10,690
213
polk county florida
Yesterday at 9:01 PM
#4
  • Yesterday at 9:01 PM
  • #4
You check for codes?
You're already throw'n parts at it, this is a common complaint and the diagnostic procedure in here:

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...
www.stangnet.com
Do what the directions say, don't jump around just because you installed new parts, they could be bad outta da box.
Best I can do cause we don't know what's been done or aftermarket parts.
 
Reactions: DadLife0724 and nickyb

CAMTWO1070

Active Member
Dec 17, 2021
251
83
38
NY
Today at 7:29 PM
#5
  • Today at 7:29 PM
  • #5
miser143 said:
Does eny one know what can the problem be this is on cold start. 1991 mustang gt 5.0 .tps is on .98v . New module new spark plug new idle control valve. Coil is good. Timing is done engine cooling temperature sensor is new .
Click to expand...
Sounds like a bad or failing ACT and ECT sensor.....New means nothing if its faulty or not calibrated right.

Theyre easy to test using a digital voltage meter and a thermometer to read coolant temps to coinside with voltage.



The other thing that affects startup is the BAP sensor , EGR sensor and the MAF flow....

Another possibility is needing your ECU rebuilt....I use ECU Exchange.

Good Luck
 
You must log in or register to reply here.

Similar threads

M
Idle control problems
  • miser143
  • Aug 28, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
2
Views
153
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Aug 29, 2026
DadLife0724
G
Idle surging after warm up
  • GALLY3309
  • Jun 10, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
1
Views
207
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 10, 2026
Noobz347
B
Help! Fox with idle issues
  • bbarton
  • Sep 11, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
7
Views
220
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Sep 12, 2026
AeroCoupe
F
Fox 1990 Mustang GT 5.0 A9L – Engine suddenly shuts off but immediately restarts when key turned
  • FishermansFriend
  • Aug 9, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
16
Views
579
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Aug 30, 2026
General karthief
S
Fox '87 GT can't get to stay running
  • spilly
  • Mar 29, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2
Replies
27
Views
1K
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 20, 2026
spilly
S
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
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?