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

Engine 1990 GT Randomly Dies is undriveable

  • Thread starter Thread starter 84blkstang
  • Start date Start date Sep 14, 2020

84blkstang

Member
Jun 4, 2003
544
1
18
Springfield MO
Sep 14, 2020
#1
  • Sep 14, 2020
  • #1
I have a 1990 GT, 306 H/C/I 5 speed 24lb injectors CAI, C&L mass air meter. it has the AL9 CPU with a BAMA tuning chip.

A little history.

During COVID quarantine I decided to start working on the car again after not driving it much. It was basically undriveable and would die randomly and not start. I could not pinpoint a precipitating factor that would cause it to die, but I found the starter cable was pulled out of the eyelet connector, but surrounded in heatshrink which made it hard to see so I replaced the cable with new ends.

Fast forward
I pulled the engine while focused on possible electrical issues causing it to die.

ELECTRICAL FIXES
Replaced the starter cable
Replaced the alternator cable
New starter
I went through and hid the entire wiring harness I replaced all the cheap or broken connectors with soldered/heatshrinked eyelets,
I re wrapped the entire harness with new loom.
cleaned each salt and pepper shaker and replaced the engine, and electrical grounds.
New speed sensor connector
Added a taurus electric fan with the FAL controller--> works awesome BTW
Motor
New distributor cap and Roto bug
New water pump
New Coil
New throttle body, egr and spacer gaskets
New valve covers with vacuum new hoses and PCV valve
New plug wires
New LMR fenderwell CAI
new harmonic balancer
Body
New grounds
new starter solenoid
new engine to body ground
New front Shocks

The only code I get is 11, TPS is 0.98v Fuel pressure with line off is 38psi, timing is 12*,

I'm at a loss at what else to look for. If I drive it down the road it does great then randomly dies, sometimes you can feather the throttle and it will stay running. Sometimes when it dies it wont start right back up without holding the throttle open like its running out of gas, but I know there is at least 5 gallons of gas in the tank.
 

jrichker

StangNet's favorite TOOL
In Remembrance. Thank you for your contributions
Mar 10, 2000
27,512
2,813
234
Dublin GA
Sep 14, 2020
#2
  • Sep 14, 2020
  • #2
84blkstang said:
I have a 1990 GT, 306 H/C/I 5 speed 24lb injectors CAI, C&L mass air meter. it has the AL9 CPU with a BAMA tuning chip.

A little history.

During COVID quarantine I decided to start working on the car again after not driving it much. It was basically undriveable and would die randomly and not start. I could not pinpoint a precipitating factor that would cause it to die, but I found the starter cable was pulled out of the eyelet connector, but surrounded in heatshrink which made it hard to see so I replaced the cable with new ends.

Fast forward
I pulled the engine while focused on possible electrical issues causing it to die.

ELECTRICAL FIXES
Replaced the starter cable
Replaced the alternator cable
New starter
I went through and hid the entire wiring harness I replaced all the cheap or broken connectors with soldered/heatshrinked eyelets,
I re wrapped the entire harness with new loom.
cleaned each salt and pepper shaker and replaced the engine, and electrical grounds.
New speed sensor connector
Added a taurus electric fan with the FAL controller--> works awesome BTW
Motor
New distributor cap and Roto bug
New water pump
New Coil
New throttle body, egr and spacer gaskets
New valve covers with vacuum new hoses and PCV valve
New plug wires
New LMR fenderwell CAI
new harmonic balancer
Body
New grounds
new starter solenoid
new engine to body ground
New front Shocks

The only code I get is 11, TPS is 0.98v Fuel pressure with line off is 38psi, timing is 12*,

I'm at a loss at what else to look for. If I drive it down the road it does great then randomly dies, sometimes you can feather the throttle and it will stay running. Sometimes when it dies it wont start right back up without holding the throttle open like its running out of gas, but I know there is at least 5 gallons of gas in the tank.
Click to expand...
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.
 
Reactions: General karthief

Blown88GT

Founding Member
Nov 13, 1999
2,283
524
164
Palm Beach Gardens, FL
Sep 16, 2020
#3
  • Sep 16, 2020
  • #3
84blkstang said:
...
The only code I get is 11, TPS is 0.98v Fuel pressure with line off is 38psi, timing is 12*,

I'm at a loss at what else to look for. If I drive it down the road it does great then randomly dies, sometimes you can feather the throttle and it will stay running. Sometimes when it dies it wont start right back up without holding the throttle open like its running out of gas, but I know there is at least 5 gallons of gas in the tank.
Click to expand...
Could be the fuel pump is bad.
You need to monitor fuel pressure under load. It can be good at idle but fall off under load.
 

84blkstang

Member
Jun 4, 2003
544
1
18
Springfield MO
Nov 2, 2020
#4
  • Nov 2, 2020
  • #4
Update: I think its the fuel pump.

I had a nice day away from clinical and I did some diagnostic testing with my new fuel pressure gauge. The fuel pump is pushing 300ml/min through the gauge overflow I measured it three separate times and it averages 69-75cc/15 seconds x 4 = 300ml min x 60 minutes =18000ml/1000 = 18Lph
When I rev the engine it drops the fuel PSI from 36 to 20 and at one time it spuddered and dropped to 10psi. So looks like I'm dropping the tank to replace it unless someone else thinks of any other great ideas.
 
Reactions: Potomus Pete

HemiRick

I'd be looking at jacking under the house
Jun 28, 2020
723
272
73
Memphis TN
Nov 2, 2020
#5
  • Nov 2, 2020
  • #5
No if your pressure is dropping that low thats the problem no doubt
 
Reactions: 84blkstang

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,892
10,551
203
polk county florida
Nov 2, 2020
#6
  • Nov 2, 2020
  • #6
Unless for some reason the fuel pump is losing voltage.
But I do think replacing the fuel pump is a good idea along with the filter.
 
Reactions: 84blkstang

84blkstang

Member
Jun 4, 2003
544
1
18
Springfield MO
Nov 2, 2020
#7
  • Nov 2, 2020
  • #7
HemiRick said:
No if your pressure is dropping that low thats the problem no doubt
Click to expand...
Thanks, I figured that was it. The PSI held steady at first then after a few minutes it dropped. Im Hoping it makes the car driveable again
 

Blown88GT

Founding Member
Nov 13, 1999
2,283
524
164
Palm Beach Gardens, FL
Nov 3, 2020
#8
  • Nov 3, 2020
  • #8
84blkstang said:
Thanks, I figured that was it. The PSI held steady at first then after a few minutes it dropped. Im Hoping it makes the car driveable again
Click to expand...
It will. They had me chasing all the electrical junk when it was the fuel pump & only the fuel pump.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,892
10,551
203
polk county florida
Nov 3, 2020
#9
  • Nov 3, 2020
  • #9
Blown88GT said:
It will. They had me chasing all the electrical junk when it was the fuel pump & only the fuel pump.
Click to expand...
'they' who???
 
You must log in or register to reply here.

Similar threads

F
2004 Mustang GT – Fuel Pump Not Priming
  • Fayio
  • Apr 22, 2026
  • SN95 4.6L Mustang Tech
Replies
7
Views
244
SN95 4.6L Mustang Tech Apr 27, 2026
n0v8or
N
B
No spark. 1990 foxbody 5.0 gt
  • Boogi
  • Nov 16, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
0
Views
174
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Nov 16, 2025
Boogi
B
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
781
Fox 5.0 Mustang Tech Nov 9, 2025
Mustang5L5
F
Electrical From scratch: alternator wiring
  • fox racer v2
  • Jun 23, 2025
  • Fox 5.0 Mustang Tech
Replies
0
Views
560
Fox 5.0 Mustang Tech Jun 23, 2025
fox racer v2
F
B
2000 GT idle
  • Bigbehr7
  • Apr 25, 2025
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
7
Views
324
1996 - 2004 SN95 Mustang -General/Talk- Jun 7, 2025
Bigbehr7
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?