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

Intermittent Issues With 85 Gt

  • Thread starter Thread starter Mike1970
  • Start date Start date Jul 2, 2013
M

Mike1970

New Member
Jun 28, 2013
7
0
1
indiana
Jul 2, 2013
#1
  • Jul 2, 2013
  • #1
Hello 5.0 guys and gals. I'm new to the forum and new to the mustang. I bought a 1985 GT with 94,000 on it. it's all stock exept for the rear gears (373) and a B&M shifter for the AOD trans.
I bought the car from a 65 yr old man who had the car for 21 years. Great car and my favorite car as a teenage kid growing up.

The problem the car has is. periodically the car stumbles and runs rough at part throttle. When this happens it feels as if the car is flooding it's self. I can floor the car and it kicks the trans down a gear and runs like normal. It will also idle normal. Then as soon as i take off again it stumbles at part throttle.

The fix is to switch the ign key off, then back on (while driving) and problem solved. It might do it again the next time i drive it, or not again the next 5 times i drive it.

No check eng light comes on. The car has a new tune up with car,rotor,wires. Has new fuel pump,pick up and sock, has new ign key. All done right before i bought it.

Any suggestion would be greatly appreciated.

Mike
 

billison

I like tinted tail
15 Year Member
Feb 27, 2006
2,607
1,094
184
stl
Jul 2, 2013
#2
  • Jul 2, 2013
  • #2
Last tune up? Is it running rich?
 
M

Mike1970

New Member
Jun 28, 2013
7
0
1
indiana
Jul 2, 2013
#3
  • Jul 2, 2013
  • #3
from the reciepts i have the last tune up was 3,000 miles ago. The car runs great until this happens. Just so happened on my way home again. It again idled fine, ran terrible at part throttle, floor the car ant it goes like normal. I can stop and the car idles normal. As soon as i take off (light throttle) all was good till 1000 rpm's. Runs bad as in it seems either out of fuel or way too much fuel. Floor the car and it's fine. The only way to fix the car is to shut the ign key off and back on. Fixes the problem everytime. I don't stop , just a quick off/on of the key and it's good to go.

thanks for the help..
I just got a manual and see there's a fuel regulator on the top of the efi ? i'm wondering if it's getting stuck and making the car rich at part throttle ? Just a guess though
 

billison

I like tinted tail
15 Year Member
Feb 27, 2006
2,607
1,094
184
stl
Jul 2, 2013
#4
  • Jul 2, 2013
  • #4
Is it still the cfi stuff or has it been swapped out for a proper carb? Because the cfi unit used on the 85 aod cars is problematic. Not hard to swap out though.
 
M

Mike1970

New Member
Jun 28, 2013
7
0
1
indiana
Jul 2, 2013
#5
  • Jul 2, 2013
  • #5
still the stock cfi. I would gladly swap it out if i could keep my cruise control and the trans would still operate properly.
would you have a link to the swap by chance ?

thank you for helping.
 

billison

I like tinted tail
15 Year Member
Feb 27, 2006
2,607
1,094
184
stl
Jul 2, 2013
#6
  • Jul 2, 2013
  • #6
I don't have a link, but I did one once and needed a intake, carb, distributor , and regulator . I did a one wire hei dizzy. This was years ago.
 

billison

I like tinted tail
15 Year Member
Feb 27, 2006
2,607
1,094
184
stl
Jul 2, 2013
#7
  • Jul 2, 2013
  • #7
And a kick down table for the tranny and new throttle cable.

Instant increase in power and it just drove better
 
M

Mike1970

New Member
Jun 28, 2013
7
0
1
indiana
Jul 2, 2013
#8
  • Jul 2, 2013
  • #8
thanks for the info. i will start looking into it.

Mike
 
R

rogerblose

Member
Jan 11, 2007
53
11
19
Jul 4, 2013
#9
  • Jul 4, 2013
  • #9
Check your EGR valve for carbon build up. Clean it / replace if bad. I have an 1988 GT that had a stumble and after a full tune up did not fix the problem, I found my 60K EGR valve was caked with carbon. Problem solved with a good cleaning with carb cleaner.
 
M

Mike1970

New Member
Jun 28, 2013
7
0
1
indiana
Jul 6, 2013
#10
  • Jul 6, 2013
  • #10
thanks roger. I found and fixed the problem. The pre cat o2 sensor was unplugged. I replaced it with a new one (after the connector melted on the exhaust) and no more rough part throttle issues and gas mileage has increased.
thanks for all the help and suggestions
 
You must log in or register to reply here.

Similar threads

P
Fuel New Eldebrock 1406 problems 1985 GT 5.0
  • Paddyman
  • Oct 22, 2026
  • Fox 5.0 Mustang Tech
Replies
4
Views
160
Fox 5.0 Mustang Tech Nov 2, 2026
manicmechanic007
I
1994 Cobra - Fuel Pressure Drops Revving at Idle
  • IconicSilverGT500
  • Apr 11, 2026
  • 1994 - 1995 Specific Tech
Replies
16
Views
626
1994 - 1995 Specific Tech Apr 24, 2026
Mcmahst
D
sad day
  • davecobra2
  • Jul 13, 2026
  • What is it Worth?!?!?
Replies
2
Views
278
What is it Worth?!?!? Jul 22, 2026
davecobra2
D
T
Drivetrain TREMEC TKX 1–2 Grinding Issue at ~4,000 Miles + Poor Warranty/Customer Service Experience
  • Ttopfoxguy
  • Oct 10, 2026
  • Fox 5.0 Mustang Tech
Replies
5
Views
286
Fox 5.0 Mustang Tech Oct 15, 2026
JMG9350
J
K
Electrical 2000 GT Intermittent Engine Shutdown In Motion - DTC U1262
  • kenster1092
  • Apr 13, 2026
  • SN95 4.6L Mustang Tech
Replies
4
Views
326
SN95 4.6L Mustang Tech Apr 24, 2026
squeak93
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?