Section 09-00: Exhaust System
1994 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Component Tests

 

PINPOINT TEST A: EXHAUST LEAKAGE OR NOISE TEST

 

A1 CLAMPS AND BRACKETS 

Yes
GO to A2.

No
SERVICE or REPLACE as necessary. RESTART engine. If noise still exists, GO to A2.

 

A2 SYSTEM COMPONENTS

Yes
GO to A3.

No
REPLACE dual converter and pipe, and/or muffler as necessary. If noise still exists, GO to A3.

 

A3 EXHAUST MANIFOLD

  • Inspect exhaust manifolds for loose fasteners or cracks.
  • Is exhaust manifold OK?
Yes
GO to B1.

No
TIGHTEN fasteners to specification or REPLACE exhaust manifold . REFER to specific engine section in this manual.

 

PINPOINT TEST B: RESTRICTED EXHAUST SYSTEM

 

B1 VISUAL INSPECTION 

  • Is the exhaust system visually OK?
Yes
GO to B2.

No
REPLACE any collapsed exhaust components. GO to B2.

 

B2 VACUUM TEST (Gasoline engine only)

  • Attach Rotunda Vacuum Gauge 059-00008 or equivalent to the intake manifold vacuum source.
  • Hook up Rotunda Tachometer 059-00007 or equivalent.
  • Start engine and gradually increase speed to 2000 rpm with transmission in neutral.
  • Is neutral vacuum above 53.8 kPa (16 in-Hg)?
Yes
REFER to Powertrain Control/Emissions Diagnosis Manual— lack of power.

No
GO to B3.

 

B3 VACUUM TEST—EXHAUST DISCONNECTED (Gasoline engine only)

  • Turn engine OFF.
  • Disconnect exhaust system at exhaust manifolds .
  • Repeat vacuum test.
  • Is the manifold vacuum above 53.8 kPa (16 in-Hg)?
Yes
GO to B4.

No
GO to B5.

 

B4 VACUUM TEST—CATALYTIC CONVERTER(S) ON, MUFFLER(S) OFF (Gasoline engine only)

  • Turn engine OFF.
  • Reconnect exhaust system at exhaust manifolds .
  • Disconnect mufflers .
  • Repeat vacuum test.
  • Is the manifold vacuum above 53.8 kPa (16 in-Hg)?
Yes
REPLACE muffler and RETEST.

No
REPLACE dual converter and pipe and inspect muffler to be sure catalyst debris has not entered muffler .

 

B5 EXHAUST MANIFOLD RESTRICTED

  • Remove the exhaust manifolds . Inspect the ports for casting flash by dropping a length of chain into each port. Do not use a wire or light to check ports. The restriction may be large enough for them to pass through but small enough to cause excessive back pressure at high engine rpm.
  • Is restriction OK?
Yes
REFER to Powertrain Control/Emissions Diagnosis Manual— lack of power.

No
REMOVE casting flash. If flash cannot be removed, REPLACE exhaust manifolds and RETEST.