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

misfires when cold/ surge idle

  • Thread starter Thread starter vanwilder692
  • Start date Start date Jun 10, 2006

vanwilder692

New Member
Jun 10, 2006
9
0
1
Youngstown Ohio
Jun 10, 2006
#1
  • Jun 10, 2006
  • #1
i have a 1989 lx sport with 140,000 on the car, i bought it in 2001 with around 92,000 on it. for five years now the car will have a surge in the idle quality that will accelerate the car, or it will misfire like it has no fuel on cold start up. i have changed the following:
1. fuel filter
2. fuel pressure regulator
3. tps
4. tfi
5 coils, caps, rotors, plugs wires like every three months
6. mass air flow
7 egr vacuum sensor
8 egr valve
9 pcv valve
10. idle air control
11. air check valve
12. air charge sensor
13. coolant temp sensor
14. o2 sensor
15. clean throttle body
the only thing i have not changed is the fuel pump, fuel filters, or the map sensor. the original motor was replaced in 1996 by the dealer and the original owner said ever since then it has had the idle problem with no luck fixing it. the fuel gauge has never worked on the car since i had it. the check engine codes will throw either a lean condition while de-celerating, or hot idle, or will throw an egr code but has had three new egr valves on it. im about to sell the car and would like to find out really whats wrong with this car. i am thinking it has been possessed. i have dumped so much money into! here is the kicker, it really misfires when it is wet. now you can sit and dump gallons of water onto the plug wires cap coil and tfi with not even a hesitation or a back fire. but dump a glass on water down behind the hood where the wipers are as to let the water run down the firewall, thats when it will misfire and chug like its getting no gas. but take it to the dealer or another garage and they cannot find anything wrong, it wont even throw a code. so im at my last nerve.
 

jrichker

StangNet's favorite TOOL
In Remembrance. Thank you for your contributions
Mar 10, 2000
27,512
2,813
234
Dublin GA
Jun 10, 2006
#2
  • Jun 10, 2006
  • #2
Post the codes & See the sticky "Help me create the Surging Idle Checklist" at the top of the forum for help with your idle problems. The first most contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.
 

Bad92GT

The 5 Minute Plan Man
Jun 10, 2004
492
0
0
SC
Jun 10, 2006
#3
  • Jun 10, 2006
  • #3
map sensor... 75% sure.. does that in one of my cars.. as it got hotter outside it stoped
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
33
129
Jun 10, 2006
#4
  • Jun 10, 2006
  • #4
Ironman92GT said:
map sensor... 75% sure.. does that in one of my cars.. as it got hotter outside it stoped
Click to expand...
His 89 should be MAF (ergo no MAP sensor). Nice thought though.
 

OonDeanisS

Founding Member
Jun 16, 2002
902
1
19
Danbury, CT
Oct 20, 2006
#5
  • Oct 20, 2006
  • #5
well i have the exact same problem in my 90, which has a baro sensor... so i hope that fixes it
 

vanwilder692

New Member
Jun 10, 2006
9
0
1
Youngstown Ohio
Oct 29, 2006
#6
  • Oct 29, 2006
  • #6
OonDeanisS said:
well i have the exact same problem in my 90, which has a baro sensor... so i hope that fixes it
Click to expand...


You win!!! thanks alot that was what it was. my BARO sensor was bad causing the car to idle rough while it is either cold or wet outside.
 

1988WHTGT

Member
Mar 31, 2005
270
0
17
Guyton, GA
Oct 29, 2006
#7
  • Oct 29, 2006
  • #7
Where is the BARO sensor located? My car is converted to MAF so is it where the MAP used to be?
 

jrichker

StangNet's favorite TOOL
In Remembrance. Thank you for your contributions
Mar 10, 2000
27,512
2,813
234
Dublin GA
Oct 30, 2006
#8
  • Oct 30, 2006
  • #8
1988WHTGT said:
Where is the BARO sensor located? My car is converted to MAF so is it where the MAP used to be?
Click to expand...
Yes.

This is not the best picture, but it helps... Look for #45 on the picture.

View attachment 428362

http://www.leemotorsports.com/f350/50enginepartsguide.JPG
 

1988WHTGT

Member
Mar 31, 2005
270
0
17
Guyton, GA
Oct 30, 2006
#9
  • Oct 30, 2006
  • #9
Thanks, thats what I thought
 
You must log in or register to reply here.

Similar threads

M
Help! 2003 GT misfire when hot
  • Modular03
  • Feb 10, 2026
  • SN95 4.6L Mustang Tech
Replies
4
Views
354
SN95 4.6L Mustang Tech Feb 13, 2026
Mustang5L5
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
778
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
860
Fox 5.0 Mustang Tech Oct 31, 2025
keel
K
Resolved Need some assistance. Holley Terminator X alongside H/C/I. Very rough/inconsistent idle
  • karhoot
  • Jun 6, 2026
  • Fox 5.0 Mustang Tech
Replies
0
Views
79
Fox 5.0 Mustang Tech Jun 6, 2026
karhoot
K
C
Engine Idle cuts out
  • claypoolxx
  • Mar 7, 2026
  • Fox 5.0 Mustang Tech
  • 2
Replies
22
Views
616
Fox 5.0 Mustang Tech Jun 5, 2026
KRUISR
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?