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

Vaccuum problem

  • Thread starter Thread starter James Czebiniak
  • Start date Start date Apr 6, 2005
J

James Czebiniak

New Member
Oct 26, 2003
5
0
0
Schenectady, NY
Apr 6, 2005
#1
  • Apr 6, 2005
  • #1
Need some input with a vaccuum problem. Will try to keep this short.
RebBuilt an 89GT 5.0 bored .030, b cam, new lifters, comp cams 1.7 roller rockers, new stock heads slightly exhaust ported.
put engine together. Had a major vaccuum leak and it ran terrible. Once I found the leak (forgot to plug in PCV valve) it smoothed out and idled fine.
was sent a bad set of FMS lifters from Summit. Had to remove upper and lower intake. Got new lifters, put it back together and it runs like it has the leak again except this time all vaccuum lines are connected correctly.
I get almost no vaccuum at idle. It idles like it has a major lift cam with about 20 degrees overlap. Burns a lot of fuel because the computer cannot figure out what is going on. I have had 4 guys look at it and listen and no one can find a leak.
If you speed up engine to about 1500 rpm you start getting vaccuum.

pulled off upper intake again and the gasket looks fine. No loose hoses no obvious leaks.

Anyone have any advice on this.
Feel free to email jczebin1@nycap.rr.com
 
S

ss93cobra

Founding Member
Apr 10, 2002
1,422
1
0
Wilmington NC
Apr 6, 2005
#2
  • Apr 6, 2005
  • #2
I know this doesn't help much, but if you had a vacuum issue that you corrected by installing the pcv valve, tore it down, and now have the same problem, the first place I'd look is with what you've done. Double check all the lines and fittings that are involved in the intake removal to find your problem. I'm not trying to sound like a smart ass so please don't take offense. If it was great before you touched it, it has to be something you've done. Your cam specs and lifters should be a decent streetable combo.
Good luck.
 

DMAN302

My mom says thanks for the pearl necklace.
Nov 8, 2003
2,120
2
59
windsor, Canada
Apr 6, 2005
#3
  • Apr 6, 2005
  • #3
Check the PCV grommet a poor seal there is a vac leak. Also did you get the grounds all back...including the hego (spelling) orange ground wire often tied to a intake bolt. That ground is for the O2 sensors and can cause issues.
 
You must log in or register to reply here.

Similar threads

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
101
Fox 5.0 Mustang Tech Jun 6, 2026
karhoot
K
H
Ongoing Battle With Hydraulic Lifters
  • hailer06
  • Jun 8, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
7
Views
313
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 9, 2026
Noobz347
Engine Gas in my oil
  • limp
  • Jun 15, 2025
  • Fox 5.0 Mustang Tech
  • 2
Replies
35
Views
1K
Fox 5.0 Mustang Tech May 16, 2026
Mindseye007
M
Engine Unexplainable Exhaust Pop and Gurgle
  • Mrnissen122
  • Feb 14, 2026
  • Fox 5.0 Mustang Tech
Replies
12
Views
589
Fox 5.0 Mustang Tech Feb 18, 2026
Noobz347
J
Emission problems
  • jls.zmmr
  • Feb 5, 2026
  • 1994 - 1995 Specific Tech
Replies
2
Views
248
1994 - 1995 Specific Tech Feb 7, 2026
AeroCoupe
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?