1996 Bronco/F-Series

Section 09-00: Exhaust System

1996 F-150, F-250, F-350, F-Super Duty, Bronco and Motorhome Chassis Vehicles Workshop Manual

DIAGNOSIS AND TESTING

Pinpoint Tests

PINPOINT TEST A: NOISY OR LEAKING EXHAUST

A1 CLAMPS AND BRACKETS

Check for broken or loose clamps and/or brackets.

Are clamps and brackets OK?

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

A2 SYSTEM COMPONENTS

Check system components for punctures, split seams or improper welds.

Are system components OK?

Yes	No
GO to A3.	REPLACE worn or damaged components as necessary. If noise still exists, GO to A3.

A3 EXHAUST MANIFOLD

Inspect exhaust manifold for loose fasteners or cracks, missing or loose exhaust back pressure (EBP) tubing, fitting or sensor.

Is exhaust manifold OK?

Yes	No
GO to B1 (gasoline engines) or C1 (diesel engines).	TIGHTEN fasteners to specification or REPLACE exhaust manifold. REFER to Section 03-01A, Section 03-01B, Section 03-01C, or Section 03-01D.

PINPOINT TEST B: RESTRICTED EXHAUST SYSTEM

B1 VACUUM TEST (GASOLINE ENGINES ONLY, EXCEPT 7.5L)

Attach a Rotunda Vacuum/Pressure Tester 164-R0253 or equivalent to the intake manifold vacuum source.
Hook up Rotunda 88 Digital Multimeter 105-R0053 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	No
REFER to Powertrain Control/Emissions Diagnosis Manual OBDI or OBDII.	GO to B2.

B2 VACUUM TEST — EXHAUST DISCONNECTED (GASOLINE ENGINES ONLY, EXCEPT 7.5L)

Turn engine off.
Disconnect exhaust system at manifold(s).
Repeat vacuum test.

Is the manifold vacuum above 53.8 kPa (16 in/Hg)?

Yes	No
GO to B3.	GO to B4.

B3 VACUUM TEST — EXHAUST CATALYTIC CONVERTER(S) ON, MUFFLER(S) OFF (GASOLINE ENGINES ONLY, EXCEPT 7.5L)

Turn engine off.
Reconnect exhaust system at exhaust manifold(s).
Disconnect muffler.
Repeat vacuum test.

Is the manifold vacuum above 53.8 kPa (16 in/Hg)?

Yes	No
REPLACE muffler and RETEST.	REPLACE catalytic converter and INSPECT muffler to be sure converter debris has not entered muffler.

B4 EXHAUST MANIFOLD RESTRICTED

Remove the exhaust manifold(s). 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.

Are ports unrestricted?

Yes	No
REFER to Powertrain Control/Emissions Diagnosis Manual OBDI or OBDII. — Lack of Power.	REMOVE casting flash. If flash cannot be removed, REPLACE exhaust manifold and RETEST.

PINPOINT TEST C: RESTRICTED EXHAUST SYSTEM (DIESEL ENGINE)

C1 DIAGNOSTIC TROUBLE CODE (DTC)

Visually inspect for kinked or damaged exhaust pipes, replace as required.
Connect Rotunda New Generation Star (NGS) Tester 007-00500 or equivalent to DLC and retrieve DTCs.

Is Diagnostic Trouble Code 0478 received?

Yes	No
GO to C2.	Problem is not exhaust system-related. REFER to Powertrain Control/Emissions Diagnosis Manual OBDI or OBDII.

C2 VERIFY EXHAUST BACK PRESSURE (EBP) SENSOR SIGNAL RETURN (DI TURBO DIESEL ONLY)

Connect Rotunda 104-Pin Breakout Box 014-00950 or equivalent.
Key on engine running at wide open throttle (WOT), engine at normal operating temperature.
Measure voltage between Pin 30 and Pin 91.

Is voltage greater than 1.9v?

Yes	No
GO to C3.	Concern is intermittent electrical problem. REFER to Powertrain Control/Emissions Diagnosis Manual OBDI or OBDII.

C3 EXHAUST SYSTEM TEST

Turn engine off.
Disconnect exhaust charge pipe from turbocharger.
Make sure exhaust back pressure butterfly valve is open all the way.
Put turbo screen in place.
Key on, engine running at wide open throttle (WOT).
Measure voltage between Pin 30 and P 91.

Is voltage greater than 1.9v?

Yes	No
CHECK EBP circuit. REFER to Powertrain Control/Emissions Diagnosis Manual OBDI or OBDII.	GO to C4.

C4 CATALYTIC CONVERTER TEST

Turn engine off.
Reconnect exhaust charge pipe to turbocharger.
Disconnect muffler pipe from the catalytic converter.
Key on, engine running at wide open throttle (WOT).
Measure voltage between Pin 30 and Pin 91.

Is voltage greater than 1.9v?

Yes	No
REPLACE the catalytic converter.	REPLACE muffler.