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

Engine Wont idle and light backfire

  • Thread starter Thread starter Darius88
  • Start date Start date Nov 6, 2023
  • Tags Tags
    5.0 gt issues modded mustang 1990
D

Darius88

Member
Apr 5, 2022
8
3
13
North Carolina
Nov 6, 2023
#1
  • Nov 6, 2023
  • #1
I have a 1990 5.0 ho that won't idle for nothing and keeps lightly backfiring . It has new plugs,wires,injectors,distributor cap and rotor,fuel pump . The engine is slightly modded with e303 cam upgraded rocker arms and bored .40 over. I have messed around with the distributor and found good spot that itll run in but the throttle has to be held open for it to keep running. Currently the throttle cable isn't hooked up. I have to remove the egr block so it will not hit my tall valve covers.
I will try to post a video, but it's being a paiin and saying every file is too big
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
5,826
3,956
183
Claremore, OK
Nov 6, 2023
#2
  • Nov 6, 2023
  • #2
Have you pulled codes and done a base idle reset? Have you done any other trouble shooting like checking the TPS voltage with the throttle body closed and checked the voltage as the throttle is opened to WOT?
 
D

Darius88

Member
Apr 5, 2022
8
3
13
North Carolina
Nov 6, 2023
#3
  • Nov 6, 2023
  • #3
I have pulled codes the only one is just a egr code. I'm new to obd 1 and do not know how to preform base idle reset but I will look into it
 

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,871
10,542
203
polk county florida
Nov 6, 2023
#4
  • Nov 6, 2023
  • #4

Help me create the "Surging Idle Checklist"

Updated 05 July 2022 to add rough idle when cold and smooth idle when up to normal operating temperature. See the EGR tech information, section #15 for more help. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank...
www.stangnet.com
This will show you how to identify idle/stall issues by checking things in order, don't jump around, do the steps one by one, you may have more than one issue I suspect. Fallow the steps even if you've replaced the part, lots of junk on the market now.
 
You must log in or register to reply here.

Similar threads

1
Engine 91 mustang 302 Low acceleration car backfires pops and acts like it doesn’t want to take fuel
  • 1991Fox5.0
  • Oct 4, 2025
  • Fox 5.0 Mustang Tech
Replies
16
Views
992
Fox 5.0 Mustang Tech Oct 6, 2025
1991Fox5.0
1
J
MEED HELP!! 86 mustang
  • Jacob0121
  • Jan 23, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
6
Views
310
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Apr 25, 2026
CAMTWO1070
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
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
759
Fox 5.0 Mustang Tech Nov 9, 2025
Mustang5L5
B
No spark. 1990 foxbody 5.0 gt
  • Boogi
  • Nov 16, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
0
Views
171
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Nov 16, 2025
Boogi
B
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?