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

Vacuum Leak???

  • Thread starter Thread starter Bullitt
  • Start date Start date Oct 7, 2006

Bullitt

Packin' Heat
Founding Member
Jan 13, 2000
2,743
0
47
Houston, TX
Oct 7, 2006
#1
  • Oct 7, 2006
  • #1
I've got a '67 Mustang I just recently converted to EFI using a Fox harness. Here's a listing of the parts in it:

Victor EFI Intake
Trick flow Heads
Lunati Cam - 218/228 @ .050 w/ .536 lift
Long tube headers (O2 sensors in the collectors)
BBK TB (70mm)
Ford 30 lb/hr injectors
Pro-M 76mm TB calibrated for 30 lb injectors
Stock Distributor with MSD box, initial timing at 15 degrees.
A9P computer (car is manual however)
No EGR or Canister Purge

All of the electronics are brand-new with the exception of the mass-air meter and the computer.

Problem I'm having is the vacuum at idle is only 4" and if I rev the engine, the RPM will hang around 2000-3000 RPM and settle back down to idle after a few seconds. At 3000 RPM, it's pulling 20" of vacuum. I've sprayed brake cleaner at the lower manifold/head gasket, upper plenum gasket, TB gasket, solenoid gasket and the engine doesn't rev up like any are leaking.

Idle is fairly steady at 800 RPM (+/- 100 RPM), but if I let it idle for a while it'll gradually slow down and eventually try to die. Vacuum is steady the whole time, not jumping around at at.

Codes out of the computer are:
34, 67, 81, 82, 84, 85

I've got one of the EGR simulators, but I think it may be defective since it's spitting out 34 and 84...

I'm really at a loss guys, please help!!
 

Bullitt

Packin' Heat
Founding Member
Jan 13, 2000
2,743
0
47
Houston, TX
Oct 7, 2006
#2
  • Oct 7, 2006
  • #2
Oh and it does this with or without the Idle Air solenoid connected.
 

Bullitt

Packin' Heat
Founding Member
Jan 13, 2000
2,743
0
47
Houston, TX
Oct 8, 2006
#3
  • Oct 8, 2006
  • #3
anyone???
 
You must log in or register to reply here.

Similar threads

7
Engine Random hanging idle
  • 706 Saleen
  • Feb 11, 2026
  • Fox 5.0 Mustang Tech
Replies
9
Views
435
Fox 5.0 Mustang Tech Feb 19, 2026
86HO5.0
8
S
Engine Stalls when downshifting/coasting
  • Scott_S
  • Nov 5, 2025
  • Fox 5.0 Mustang Tech
Replies
11
Views
645
Fox 5.0 Mustang Tech Nov 6, 2025
Mustang5L5
Fox Xtremely high fuel consumption
  • PonyGTrider
  • Apr 11, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 9 10 11
Replies
213
Views
3K
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- May 9, 2026
PonyGTrider
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
720
Fox 5.0 Mustang Tech Nov 9, 2025
Mustang5L5
C
Engine Code 13 and high idle
  • CmdrDerp
  • Dec 14, 2024
  • Fox 5.0 Mustang Tech
Replies
17
Views
800
Fox 5.0 Mustang Tech Dec 21, 2024
manicmechanic007
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?