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

1991 5.0 Mustang Exhaust Concern

  • Thread starter Thread starter 5.0specialist
  • Start date Start date Jul 11, 2016

5.0specialist

Active Member
Jul 10, 2016
141
53
48
venice fl
Jul 11, 2016
#1
  • Jul 11, 2016
  • #1
Hello everyone. I have a 1991 mustang gt with BBK unequal length shorty headers, offroad X pipe, and steeda stainless mufflers that are identical to these, but used and a bit aged... : http://www.ebay.com/itm/Steeda-Muffl...dS7-QJ&vxp=mtr ) . I've noticed something weird when my car is idling. There is more air coming out of the driver's side tail pipe than the passenger side tailpipe. The driver's side tailpipe is also noticeably louder than the passenger side tail pipe. There are no exhaust leaks as far as I know (don't hear any leaks). The engine also runs great. No signs of a cylinder with low compression or a bad spark plug (recently changed my spark plugs using the recommended motorcraft plugs). The car runs great. Heck, it actually burns some rubber when flooring it from a dead stop with a stock AOD and 2.73 gears (it's also a convertible). These mufflers are made by Borla and are fully constructed with stainless steel. There is also noise insulation packing in these mufflers. Is this something I should worry about or is this just something that normally occurs?

Thank you,

Alexi
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,260
17,944
224
Massachusetts
Jul 11, 2016
#2
  • Jul 11, 2016
  • #2
Take a rag and carefully stuff a tailpipe one at a time. Does the exhaust flow from the other one increase? Does the engine want to stall out.

Make sure said rag is clean and free from grease/oil


Sent from my big ass iPhone 6 using Tapatalk
 
Reactions: 5.0specialist

5.0specialist

Active Member
Jul 10, 2016
141
53
48
venice fl
Jul 11, 2016
#3
  • Jul 11, 2016
  • #3
I'll try that today. Thanks
 

5.0specialist

Active Member
Jul 10, 2016
141
53
48
venice fl
Jul 11, 2016
#4
  • Jul 11, 2016
  • #4
I covered the driver's side tail pipe and a lot more air began flowing out of the passenger side tail pipe. The engine did not try to stall. Afterwards, I kept the engine at 2000 rpms (both tailpipes not covered) and my dad told me that there was still more air coming out of the driver's side tailpipe. I also noticed that the air on the driver's side is hotter than the passenger side. The X pipe still has the smog tube attached to the passenger side pipe before the cross over, which is capped by a rubber vacuum cap in the engine compartment where the smog pump hose was connected to. I wonder if that has something to do with it. This wednesday, I'm going to a mustang performance shop to get 3.73 gears installed. I'll have the guy check it out.
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,260
17,944
224
Massachusetts
Jul 11, 2016
#5
  • Jul 11, 2016
  • #5
Got a laser thermometer? Shoot it at the mufflers. I'm thinking one of them may be blocked.


Sent from my big ass iPhone 6 using Tapatalk
 
Reactions: 5.0specialist

5.0specialist

Active Member
Jul 10, 2016
141
53
48
venice fl
Jul 11, 2016
#6
  • Jul 11, 2016
  • #6
My dad has one at work that he can bring next week. Anyways, I'm getting gears installed this wednesday. I'll have the guy check it out. Thanks for your help.
 

5.0specialist

Active Member
Jul 10, 2016
141
53
48
venice fl
Jul 13, 2016
#7
  • Jul 13, 2016
  • #7
Had the gears installed today (wow, what a difference) and I took a closer looks at the exhaust. Everything is nice and snug without any leaks. I mentioned the mystery to the mechanic and he was confused by it. The steeda mufflers are made by Borla and they don't have any baffles (straight through design). What I'm thinking is that the packing in the driver's side muffler is more worn out allowing the muffler to be a bit louder and allow more air to bounce around in there and flow through. The car runs great and shows no signs of having any restriction in the exhaust.
 

5.0specialist

Active Member
Jul 10, 2016
141
53
48
venice fl
Aug 7, 2016
#8
  • Aug 7, 2016
  • #8
Well, I just used a laser temperature gun and the driver's muffler (the one that is louder and pumps out more air) is running at an average temperature of 260 degrees. The passenger side muffler (the quieter one with much less air pumping out) is averaging at 101 degrees. The pipes before the muffler (after the cross-over) have the same difference, although not as dramatic. Both pipes before the cross over read the same average temperature (240 degrees).
 
Last edited: Aug 7, 2016

5.0specialist

Active Member
Jul 10, 2016
141
53
48
venice fl
Oct 8, 2016
#9
  • Oct 8, 2016
  • #9
Just found out what the problem was. There was a large piece of catalytic converter brick jammed into the flange of the x-pipe on the passenger side, where it meets the catback. lol Just had a 2.5 inch catback installed today (using Jones Max Flow mufflers).
 
You must log in or register to reply here.

Similar threads

M
Help! 2003 GT misfire when hot
  • Modular03
  • Feb 10, 2026
  • SN95 4.6L Mustang Tech
Replies
4
Views
396
SN95 4.6L Mustang Tech Feb 13, 2026
Mustang5L5
Who the hell puts the wrong spark plugs in a 3.8L?
  • snowstang
  • Mar 25, 2026
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
12
Views
443
1996 - 2004 SN95 Mustang -General/Talk- Apr 3, 2026
LILCBRA
G
1982 Mustang GL 5.0 single to dual exhaust conversion
  • Guyton
  • Jun 27, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
15
Views
669
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jul 1, 2025
limp
S
Engine I am having trouble with the engine in my 1991 Mustang.
  • sands9330014
  • Sep 28, 2024
  • Fox 5.0 Mustang Tech
  • 2 3
Replies
47
Views
2K
Fox 5.0 Mustang Tech Apr 12, 2025
Mindseye007
Exhaust Flowmaster catback exhaust install kicking my butt....
  • 91GTstroked
  • May 20, 2023
  • Fox 5.0 Mustang Tech
Replies
5
Views
2K
Fox 5.0 Mustang Tech May 21, 2023
91GTstroked
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?